11. Commitments and Contingencies Historical Leases We lease our headquarters facility under a 15 -year lease agreement which was entered into in October 2008 , and has two five -year renewal options. The current annual base rent of the lease is $5.1 million , payable in equal monthly installments. The base rent escalates annually at a rate equal to the change in the consumer price index, as defined in the agreement, but not to exceed 5.5% in any year. We have a lease for office space in Austin, Texas which terminates on September 30, 2023, and has two five -year renewal options. The current annual base rent of the lease is $2.8 million . The base rent escalates annually between 2% and 4% based on the terms of the agreement. The rent expense is recorded on a straight-line basis over the length of the lease term. At December31, 2016 , we had a standby letter of credit of $2.0 million for a security deposit for this lease. We have provisions in our leases that entitle us to aggregate remaining leasehold improvement allowances of $5.1 million as of December31, 2016 . These amounts are being recorded as a reduction to rent expense ratably over the terms of the leases. The leasehold improvement allowances have been included in the table of operating lease commitments below as a reduction in our lease commitments ratably over the then remaining terms of the leases. The timing of the reimbursements for the actual leasehold improvements may vary from the amounts reflected in the table below. We have also received quarterly South Carolina state incentive payments as a result of locating our headquarters facility in Berkeley County, South Carolina. These amounts are recorded as a reduction of rent expense upon receipt and were $2.9 million , $2.3 million and $2.2 million for the years ended December31, 2016 , 2015 and 2014 , respectively. These quarterly state incentive payments related to our current headquarters facility ended in 2016. Total rent expense was $11.7 million , $10.3 million and $9.4 million for the years