in 2018 , we invested in our mobile operating partnership with comcast corporation , with a portion representing our equity investment in the partnership and a portion representing a prepayment of software development and related services for the mobile back office platform . as the partnership delivers services , we will reflect such services as capital or operating expense depending on the nature of services delivered . we believe spectrum-branded mobile services will drive higher sales of our core products , create longer customer lives and increase profitability and cash flow over time . as a result of growth costs associated with our new mobile product line , we can not be certain that we will be able to grow revenues or maintain our margins at recent historical rates . during the year ended december 31 , 2018 , our mobile product line increased revenues by $ 106 million , and reduced adjusted ebitda and free cash flow by approximately $ 240 million and $ 594 million , respectively . as we continue to launch our mobile service and scale the business , we expect continued negative impacts to adjusted ebitda , as well as negative working capital impacts from the timing of device-related cash flows when we provide the handset or tablet to customers pursuant to equipment installment plans . in 2019 , we intend to expand our spectrum mobile bring-your-own-device ( `` byod `` ) program across our key sales channels to include a broader set of devices . we believe our byod program will lower the cost for consumers of switching mobile carriers , and will reduce the short-term working capital impact of selling new mobile devices on installment plans . the company realized revenue , adjusted ebitda and income from operations during the periods presented as follows ( in millions ; all percentages are calculated using whole numbers . minor differences may exist due to rounding ) . replace_table_token_3_th ( a ) income from operations for the year ended december 31 , 2016 has been reduced from what was previously reported to reflect the adoption of pension accounting guidance by $ 899 million and $ 915 million on an actual and pro forma basis , respectively . adjusted ebitda is defined as consolidated net income plus net interest expense , income taxes , depreciation and amortization , stock compensation expense , loss on extinguishment of debt , ( gain ) loss on financial instruments , net , other pension benefits , other ( income ) expense , net and other operating ( income ) expenses , such as merger and restructuring costs , special charges and ( gain ) loss on sale or retirement of assets . see “ —use of adjusted ebitda and free cash flow ” for further information on adjusted ebitda and free cash flow . growth in total revenue , adjusted ebitda and income from operations was primarily due to growth in our residential internet and commercial business customers as well as an increase in advertising sales revenue primarily due to an increase in political revenue . adjusted ebitda growth was additionally affected by increases in operating costs and expenses primarily programming and , in 2018 , mobile . income from operations was also affected by changes in depreciation and amortization as well as decreases in merger and restructuring costs . 29 approximately 91 % , 91 % and 90 % of our revenues for years ended december 31 , 2018 , 2017 and 2016 , respectively , are attributable to monthly subscription fees charged to customers for our video , internet , voice and commercial services provided by our cable systems . generally , these customer subscriptions may be discontinued by the customer at any time subject to a fee for certain commercial customers . the remaining 9 % , 9 % and 10 % of revenue for fiscal years 2018 , 2017 and 2016 , respectively , is derived primarily from advertising revenues , franchise and other regulatory fee revenues ( which are collected by us but then paid to local authorities ) , vod and pay-per-view programming , installation , processing fees or reconnection fees charged to customers to commence or reinstate service , revenue from regional sports and news channels and commissions related to the sale of merchandise by home shopping services . critical accounting policies and estimates certain of our accounting policies require our management to make difficult , subjective and or complex judgments . management has discussed these policies with the audit committee of charter 's board of directors , and the audit committee has reviewed the following disclosure . we consider the following policies to be the most critical in understanding the estimates , assumptions and judgments that are involved in preparing our financial statements , and the uncertainties that could affect our results of operations , financial condition and cash flows : property , plant and equipment capitalization of labor and overhead costs valuation and impairment of property , plant and equipment useful lives of property , plant and equipment intangible assets valuation and impairment of franchises valuation and impairment of goodwill valuation , impairment and amortization of customer relationships income taxes litigation programming agreements pension plans in addition , there are other items within our financial statements that require estimates or judgment that are not deemed critical , such as the allowance for doubtful accounts and valuations of our financial instruments , but changes in estimates or judgment in these other items could also have a material impact on our financial statements . property , plant and equipment the cable industry is capital intensive , and a large portion of our resources are spent on capital activities associated with extending , rebuilding , and upgrading our cable network . story_separator_special_tag pension plans we sponsor two qualified defined benefit pension plans , the twc pension plan and the twc union pension plan ( collectively , the “ twc pension plans ” ) , that provide pension benefits to a majority of legacy twc employees . we also provide a nonqualified defined benefit pension plan for certain employees under the twc excess pension plan . as of december 31 , 2018 , the accumulated benefit obligation and fair value of plan assets for the twc pension plans was $ 3.0 billion and $ 2.9 billion , respectively , and the net underfunded liability of the twc pension plans was recorded as a $ 1 million noncurrent asset , $ 4 million current liability and $ 95 million long-term liability . as of december 31 , 2017 , the accumulated benefit obligation and fair value of plan assets for the twc pension plans was $ 3.6 billion and $ 3.3 billion , respectively , and the net underfunded liability of the twc pension plans was recorded as a $ 1 million noncurrent asset , $ 5 million current liability and $ 292 million long-term liability . 33 pension benefits are based on formulas that reflect the employees ' years of service and compensation during their employment period . actuarial gains or losses are changes in the amount of either the benefit obligation or the fair value of plan assets resulting from experience different from that assumed or from changes in assumptions . we have elected to follow a mark-to-market pension accounting policy for recording the actuarial gains or losses annually during the fourth quarter , or earlier if a remeasurement event occurs during an interim period . we use a december 31 measurement date for our pension plans . we recognized net periodic pension benefits of $ 192 million , $ 1 million and $ 813 million in 2018 , 2017 and 2016 , respectively . net periodic pension benefit or expense is determined using certain assumptions , including the expected long-term rate of return on plan assets , discount rate and mortality assumptions . we determined the discount rate used to compute pension expense based on the yield of a large population of high-quality corporate bonds with cash flows sufficient in timing and amount to settle projected future defined benefit payments . in developing the expected long-term rate of return on assets , we considered the current pension portfolio 's composition , past average rate of earnings , and our asset allocation targets . we used a discount rate of 3.68 % from january 1 , 2018 to september 30 , 2018 and 4.24 % from october 1 , 2018 to december 31 , 2018 to compute 2018 pension expense . a decrease in the discount rate of 25 basis points would result in a $ 137 million increase in our pension plan benefit obligation as of december 31 , 2018 and net periodic pension expense recognized in 2018 under our mark-to-market accounting policy . our expected long-term rate of return on plan assets used to compute 2018 pension expense was 5.75 % . a decrease in the expected long-term rate of return of 25 basis points , from 5.75 % to 5.50 % , while holding all other assumptions constant , would result in an increase in our 2019 net periodic pension expense of approximately $ 7 million . see note 18 to the accompanying consolidated financial statements contained in “ part ii . item 8. financial statements and supplementary data ” for additional discussion on these assumptions . results of operations the following table sets forth the consolidated statements of operations for the periods presented ( dollars in millions , except per share data ) : replace_table_token_4_th revenues . total revenues grew $ 2.0 billion or 4.9 % during the year ended december 31 , 2018 as compared to 2017 and grew $ 12.6 billion or 43.4 % during the year ended december 31 , 2017 as compared to 2016 . revenue growth primarily reflects increases in the number of residential internet and commercial business customers , price adjustments as well as the launch of our mobile service in 2018 offset by a decrease in limited basic video customers . the transactions increased revenues for the year ended 34 2017 as compared to 2016 by approximately $ 11.4 billion . on a pro forma basis , assuming the transactions occurred as of january 1 , 2015 , total revenue growth was 3.9 % for the year ended december 31 , 2017 as compared to the year ended december 31 , 2016. revenues by service offering were as follows ( dollars in millions ; all percentages are calculated using whole numbers . minor differences may exist due to rounding ) : replace_table_token_5_th video revenues consist primarily of revenues from basic and digital video services provided to our residential customers , as well as franchise fees , equipment service fees and video installation revenue . the increases in video revenues are attributable to the following ( dollars in millions ) : replace_table_token_6_th the increases related to rate changes were primarily due to price adjustments including promotional roll-off , service level changes and bundle revenue allocation . residential video customers decreased by 296,000 and 301,000 in 2018 and 2017 , respectively . on a pro forma basis , assuming the transactions occurred as of january 1 , 2015 , the increase in video revenues is attributable to the following ( dollars in millions ) : replace_table_token_7_th 35 the increases in internet revenues from our residential customers are attributable to the following ( dollars in millions ) : replace_table_token_8_th residential internet customers grew by 1,107,000 and 1,159,000 in 2018 and 2017 , respectively . the increases related to rate changes were primarily due to price adjustments including promotional roll-off and bundle revenue allocation . on a pro forma basis , assuming the transactions occurred as of january 1 , 2015 , the increase in

liquidity and capital resources overview we have significant amounts of debt . the principal amount of our debt as of december 31 , 2018 was $ 72.0 billion , consisting of $ 10.0 billion of credit facility debt , $ 43.0 billion of investment grade senior secured notes and $ 18.9 billion of high-yield senior unsecured notes . our business requires significant cash to fund principal and interest payments on our debt . our projected cash needs and projected sources of liquidity depend upon , among other things , our actual results , and the timing and amount of our expenditures . as we launch our new mobile services , we expect an initial funding period to grow a new product as well as negative working capital impacts from the timing of device-related cash flows when we provide the handset or tablet to customers pursuant to equipment installment plans . free cash flow was $ 2.1 billion , $ 3.7 billion and $ 4.0 billion for the years ended december 31 , 2018 , 2017 and 2016 , respectively . the decrease in free cash flow in 2018 as compared to 2017 is primarily due to an unfavorable change in working capital as well as an increase in cash paid for interest and capital expenditures . as of december 31 , 2018 , the amount available under our credit facilities was approximately $ 2.8 billion and cash on hand was approximately $ 300 million .


 Write a concise suspicious activity report of the following text delimited by triple backquotes. Return your response as a formal report which covers the key points highlighting the location,dates,entity names and account holder information in chronological order of the text.
     ```liquidity and capital resources overview we have significant amounts of debt . the principal amount of our debt as of december 31 , 2018 was $ 72.0 billion , consisting of $ 10.0 billion of credit facility debt , $ 43.0 billion of investment grade senior secured notes and $ 18.9 billion of high-yield senior unsecured notes . our business requires significant cash to fund principal and interest payments on our debt . our projected cash needs and projected sources of liquidity depend upon , among other things , our actual results , and the timing and amount of our expenditures . as we launch our new mobile services , we expect an initial funding period to grow a new product as well as negative working capital impacts from the timing of device-related cash flows when we provide the handset or tablet to customers pursuant to equipment installment plans . free cash flow was $ 2.1 billion , $ 3.7 billion and $ 4.0 billion for the years ended december 31 , 2018 , 2017 and 2016 , respectively . the decrease in free cash flow in 2018 as compared to 2017 is primarily due to an unfavorable change in working capital as well as an increase in cash paid for interest and capital expenditures . as of december 31 , 2018 , the amount available under our credit facilities was approximately $ 2.8 billion and cash on hand was approximately $ 300 million .
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 Suspicious Activity Report : in 2018 , we invested in our mobile operating partnership with comcast corporation , with a portion representing our equity investment in the partnership and a portion representing a prepayment of software development and related services for the mobile back office platform . as the partnership delivers services , we will reflect such services as capital or operating expense depending on the nature of services delivered . we believe spectrum-branded mobile services will drive higher sales of our core products , create longer customer lives and increase profitability and cash flow over time . as a result of growth costs associated with our new mobile product line , we can not be certain that we will be able to grow revenues or maintain our margins at recent historical rates . during the year ended december 31 , 2018 , our mobile product line increased revenues by $ 106 million , and reduced adjusted ebitda and free cash flow by approximately $ 240 million and $ 594 million , respectively . as we continue to launch our mobile service and scale the business , we expect continued negative impacts to adjusted ebitda , as well as negative working capital impacts from the timing of device-related cash flows when we provide the handset or tablet to customers pursuant to equipment installment plans . in 2019 , we intend to expand our spectrum mobile bring-your-own-device ( `` byod `` ) program across our key sales channels to include a broader set of devices . we believe our byod program will lower the cost for consumers of switching mobile carriers , and will reduce the short-term working capital impact of selling new mobile devices on installment plans . the company realized revenue , adjusted ebitda and income from operations during the periods presented as follows ( in millions ; all percentages are calculated using whole numbers . minor differences may exist due to rounding ) . replace_table_token_3_th ( a ) income from operations for the year ended december 31 , 2016 has been reduced from what was previously reported to reflect the adoption of pension accounting guidance by $ 899 million and $ 915 million on an actual and pro forma basis , respectively . adjusted ebitda is defined as consolidated net income plus net interest expense , income taxes , depreciation and amortization , stock compensation expense , loss on extinguishment of debt , ( gain ) loss on financial instruments , net , other pension benefits , other ( income ) expense , net and other operating ( income ) expenses , such as merger and restructuring costs , special charges and ( gain ) loss on sale or retirement of assets . see “ —use of adjusted ebitda and free cash flow ” for further information on adjusted ebitda and free cash flow . growth in total revenue , adjusted ebitda and income from operations was primarily due to growth in our residential internet and commercial business customers as well as an increase in advertising sales revenue primarily due to an increase in political revenue . adjusted ebitda growth was additionally affected by increases in operating costs and expenses primarily programming and , in 2018 , mobile . income from operations was also affected by changes in depreciation and amortization as well as decreases in merger and restructuring costs . 29 approximately 91 % , 91 % and 90 % of our revenues for years ended december 31 , 2018 , 2017 and 2016 , respectively , are attributable to monthly subscription fees charged to customers for our video , internet , voice and commercial services provided by our cable systems . generally , these customer subscriptions may be discontinued by the customer at any time subject to a fee for certain commercial customers . the remaining 9 % , 9 % and 10 % of revenue for fiscal years 2018 , 2017 and 2016 , respectively , is derived primarily from advertising revenues , franchise and other regulatory fee revenues ( which are collected by us but then paid to local authorities ) , vod and pay-per-view programming , installation , processing fees or reconnection fees charged to customers to commence or reinstate service , revenue from regional sports and news channels and commissions related to the sale of merchandise by home shopping services . critical accounting policies and estimates certain of our accounting policies require our management to make difficult , subjective and or complex judgments . management has discussed these policies with the audit committee of charter 's board of directors , and the audit committee has reviewed the following disclosure . we consider the following policies to be the most critical in understanding the estimates , assumptions and judgments that are involved in preparing our financial statements , and the uncertainties that could affect our results of operations , financial condition and cash flows : property , plant and equipment capitalization of labor and overhead costs valuation and impairment of property , plant and equipment useful lives of property , plant and equipment intangible assets valuation and impairment of franchises valuation and impairment of goodwill valuation , impairment and amortization of customer relationships income taxes litigation programming agreements pension plans in addition , there are other items within our financial statements that require estimates or judgment that are not deemed critical , such as the allowance for doubtful accounts and valuations of our financial instruments , but changes in estimates or judgment in these other items could also have a material impact on our financial statements . property , plant and equipment the cable industry is capital intensive , and a large portion of our resources are spent on capital activities associated with extending , rebuilding , and upgrading our cable network . story_separator_special_tag pension plans we sponsor two qualified defined benefit pension plans , the twc pension plan and the twc union pension plan ( collectively , the “ twc pension plans ” ) , that provide pension benefits to a majority of legacy twc employees . we also provide a nonqualified defined benefit pension plan for certain employees under the twc excess pension plan . as of december 31 , 2018 , the accumulated benefit obligation and fair value of plan assets for the twc pension plans was $ 3.0 billion and $ 2.9 billion , respectively , and the net underfunded liability of the twc pension plans was recorded as a $ 1 million noncurrent asset , $ 4 million current liability and $ 95 million long-term liability . as of december 31 , 2017 , the accumulated benefit obligation and fair value of plan assets for the twc pension plans was $ 3.6 billion and $ 3.3 billion , respectively , and the net underfunded liability of the twc pension plans was recorded as a $ 1 million noncurrent asset , $ 5 million current liability and $ 292 million long-term liability . 33 pension benefits are based on formulas that reflect the employees ' years of service and compensation during their employment period . actuarial gains or losses are changes in the amount of either the benefit obligation or the fair value of plan assets resulting from experience different from that assumed or from changes in assumptions . we have elected to follow a mark-to-market pension accounting policy for recording the actuarial gains or losses annually during the fourth quarter , or earlier if a remeasurement event occurs during an interim period . we use a december 31 measurement date for our pension plans . we recognized net periodic pension benefits of $ 192 million , $ 1 million and $ 813 million in 2018 , 2017 and 2016 , respectively . net periodic pension benefit or expense is determined using certain assumptions , including the expected long-term rate of return on plan assets , discount rate and mortality assumptions . we determined the discount rate used to compute pension expense based on the yield of a large population of high-quality corporate bonds with cash flows sufficient in timing and amount to settle projected future defined benefit payments . in developing the expected long-term rate of return on assets , we considered the current pension portfolio 's composition , past average rate of earnings , and our asset allocation targets . we used a discount rate of 3.68 % from january 1 , 2018 to september 30 , 2018 and 4.24 % from october 1 , 2018 to december 31 , 2018 to compute 2018 pension expense . a decrease in the discount rate of 25 basis points would result in a $ 137 million increase in our pension plan benefit obligation as of december 31 , 2018 and net periodic pension expense recognized in 2018 under our mark-to-market accounting policy . our expected long-term rate of return on plan assets used to compute 2018 pension expense was 5.75 % . a decrease in the expected long-term rate of return of 25 basis points , from 5.75 % to 5.50 % , while holding all other assumptions constant , would result in an increase in our 2019 net periodic pension expense of approximately $ 7 million . see note 18 to the accompanying consolidated financial statements contained in “ part ii . item 8. financial statements and supplementary data ” for additional discussion on these assumptions . results of operations the following table sets forth the consolidated statements of operations for the periods presented ( dollars in millions , except per share data ) : replace_table_token_4_th revenues . total revenues grew $ 2.0 billion or 4.9 % during the year ended december 31 , 2018 as compared to 2017 and grew $ 12.6 billion or 43.4 % during the year ended december 31 , 2017 as compared to 2016 . revenue growth primarily reflects increases in the number of residential internet and commercial business customers , price adjustments as well as the launch of our mobile service in 2018 offset by a decrease in limited basic video customers . the transactions increased revenues for the year ended 34 2017 as compared to 2016 by approximately $ 11.4 billion . on a pro forma basis , assuming the transactions occurred as of january 1 , 2015 , total revenue growth was 3.9 % for the year ended december 31 , 2017 as compared to the year ended december 31 , 2016. revenues by service offering were as follows ( dollars in millions ; all percentages are calculated using whole numbers . minor differences may exist due to rounding ) : replace_table_token_5_th video revenues consist primarily of revenues from basic and digital video services provided to our residential customers , as well as franchise fees , equipment service fees and video installation revenue . the increases in video revenues are attributable to the following ( dollars in millions ) : replace_table_token_6_th the increases related to rate changes were primarily due to price adjustments including promotional roll-off , service level changes and bundle revenue allocation . residential video customers decreased by 296,000 and 301,000 in 2018 and 2017 , respectively . on a pro forma basis , assuming the transactions occurred as of january 1 , 2015 , the increase in video revenues is attributable to the following ( dollars in millions ) : replace_table_token_7_th 35 the increases in internet revenues from our residential customers are attributable to the following ( dollars in millions ) : replace_table_token_8_th residential internet customers grew by 1,107,000 and 1,159,000 in 2018 and 2017 , respectively . the increases related to rate changes were primarily due to price adjustments including promotional roll-off and bundle revenue allocation . on a pro forma basis , assuming the transactions occurred as of january 1 , 2015 , the increase in

