12.

Leases

We maintain operating lease agreements principally for our office spaces. We lease approximately 264,000 square feet of office space for our corporate headquarters in Franklin, Tennessee, approximately 221,000 square feet of which is subleased. This lease commenced in March 2008 and expires in February 2023. We also lease approximately 92,000 square feet of office space in Chandler, Arizona, and approximately 6,000 square feet of office space in Ashburn, Virginia. The Chandler, Arizona lease began in April 2009 and expires in April 2020.

Our corporate office lease agreement in Tennessee contains escalation clauses and provides for two renewal options of five years each at then prevailing market rates. The base rent for the initial 15-year term ranges from $4.3 million to $6.6 million per year over the term of the lease. The landlord provided a tenant improvement allowance equal to approximately $10.7 million. We record leasehold improvement incentives as deferred rent and amortize them as reductions to rent expense over the lease term.

Most of our operating leases include escalation clauses, some of which are fixed amounts, and some of which reflect changes in price indices. We recognize rent expense on a straight-line basis over the lease term. Certain operating leases contain renewal options to extend the lease for additional periods. For the years ended December 31, 2017, 2016, and 2015, rent expense under lease agreements, net of sublease income, was approximately $2.5 million, $4.2 million, and $3.7 million, respectively. Our capital lease obligations are included in long-term debt and the current portion of long-term debt.

The following table summarizes our future minimum lease payments, net of total cash receipts from subleases of $29.2 million, under all non-cancelable operating leases for each of the next five years and thereafter. As of December 31, 2017, future minimum lease payments under capital leases were not material.

(In thousands)	Operating
Year ending December 31,	Leases
2018	$	5,547
2019		5,645
2020		3,175
2021		910
2022		827
2023 and thereafter		136
Total minimum lease payments	$	16,240