Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America for interim financial reporting and the instructions to Form 10-Q and, therefore, reflect all adjustments which are, in the opinion of management, necessary for a fair statement of the results for the interim periods presented. All such adjustments are of a normal recurring nature. These interim condensed consolidated financial statements should be read in conjunction with the Consolidated Financial Statements and Notes to Consolidated Financial Statements in our Annual Report on Form 10-K for the year ended December 31, 2019 . Recent Accounting Pronouncements - Not Yet Adopted Simplifying the Accounting for Income Taxes In December 2019, the Financial Accounting Standards Board (FASB) issued amended guidance to simplify the accounting for income taxes. The guidance is effective for fiscal years beginning after December 15, 2020, including interim periods within those fiscal years. Early adoption is permitted. Certain amendments should be applied prospectively, while other amendments should be applied retrospectively to all periods presented. We are currently evaluating the timing and impact of the amended guidance on our consolidated financial statements. Disclosure Requirements for Defined Benefit Plans In August 2018, the Financial Accounting Standards Board (FASB) issued amended guidance to add, remove, and clarify disclosure requirements related to defined benefit pension and other postretirement plans. The amended guidance removes the requirements to disclose: amounts in accumulated other comprehensive income (loss) expected to be recognized as components of net periodic benefit cost over the next fiscal year; the amount and timing of plan assets expected to be returned to the entity; and the effects of a one-percentage point change in assumed health care cost trend rates. The amended guidance requires disclosure of an explanation of the reasons for significant gains and losses related to changes in the benefit obligation for the period. This guidance is effective for fiscal years ending after December 15, 2020, with early adoption permitted. The amended guidance is required to be applied on a retrospective basis to all periods presented. We are currently evaluating this guidance to determine the impact on our disclosures. Recent Accounting Pronouncements - Adopted Measurement of Credit Losses on Financial Instruments In June 2016, the FASB issued amended guidance that changes the impairment model for most financial assets and certain other instruments. For trade receivables, contract assets and other receivables, held-to-maturity debt securities, loans and other instruments, entities are required to use a current expected credit loss ("CECL") model that will immediately recognize an estimate of credit losses that are expected to occur over the life of the financial instruments that are in the scope of this update, including trade receivables. For available-for-sale debt securities with unrealized losses, entities will measure credit losses in a manner similar to current practice, except that the losses will be recognized as an allowance. The CECL model is based on relevant information about past events, including historical experience, current conditions and reasonable and supportable forecasts that affect collectability. On January 1, 2020, we adopted the new CECL standard and developed an expected impairment model based on our historical loss experience. We believe that our previous methodology to calculate credit losses is generally consistent with the new expected credit loss model and did not result in a material adjustment during the three months ended March 31, 2020. The allowance for doubtful accounts was $9.5 million and $7.2 million as of March 31, 2020 and December 31, 2019, respectively.