Commitments and Contingencies Operating Lease Commitments The Company leases office space under non-cancellable operating leases for its corporate headquarters in Austin, Texas in two adjacent buildings under separate lease agreements. Pursuant to the first of which the Company leases approximately 67 square feet of office space with an initial term that expires on April 30, 2021, with the option to extend the lease for an additional five -year term, and pursuant to the second of which the Company leases approximately 129 square feet of office space with an initial term that expires on April 30, 2028, with the option to extend the lease for an additional ten -year term. The Company also leases office space in: Lincoln, Nebraska; Des Moines, Iowa; Atlanta, Georgia; Asheville, North Carolina; and south Austin, Texas. In the second quarter of 2018, the Company vacated a portion of its south Austin office and recorded an unoccupied lease charge of $0.7 million for the remaining contractual lease payments, associated asset disposal, and related fees, less estimated sublease income. The associated lease liability of $0.2 million is expected to be paid during the succeeding twelve-month period and recorded in accrued liabilities, and the remaining portion of $0.4 million is recorded in other long-term liabilities, on the accompanying condensed consolidated balance sheet at September 30, 2018 . The Company believes its current facilities will be adequate for its needs for the current term and will evaluate its needs for expansion beyond the 2021 lease expiration. Rent expense under operating leases was $1.0 million and $1.1 million for the three months ended September 30, 2018 and 2017 , respectively, and $3.2 million and $3.3 million for the nine months ended September 30, 2018 and 2017 , respectively. Future minimum payments required under operating leases that have initial or remaining non-cancelable lease terms in excess of one year at September 30, 2018 were as follows: Operating Leases Year Ended December 31, 2018 (from October 1 to December 31) $ 1,427 2019 5,361 2020 5,364 2021 4,461 2022 3,969 Thereafter 20,677 Total commitments $ 41,259 Contractual Commitments The Company has non-cancelable contractual commitments related to the Convertible Notes and related interest, third-party products, co-location fees and other product costs. The Company is party to several purchase commitments for third-party products that contain both a contractual minimum obligation and a variable obligation based upon usage or other factors which can change on a monthly basis. The interest on the Convertible Notes is payable semi-annually on February 15 and August 15 of each year. The estimated amounts for usage and other factors are not included within the table below. Future minimum contractual commitments that have initial or remaining non-cancelable terms in excess of one year were as follows: Contractual Commitments Year Ended December 31, 2018 (from October 1 to December 31) $ 2,780 2019 14,183 2020 10,425 2021 9,096 2022 9,080 Thereafter 236,379 Total commitments $ 281,943 Legal Proceedings From time to time, the Company may become involved in legal proceedings arising in the ordinary course of its business. The Company is not presently a party to any legal proceedings that, if determined adversely to the Company, would have a material adverse effect on the Company.