NOTE 14. COMMITMENTS AND CONTINGENCIES (a) Lease Obligations In the first quarter of 2015, the Company entered into the Sixth Amendment to its corporate headquarters lease agreement in San Francisco, California, pursuant to which it leased approximately 16,000 additional square feet of office space. The Company is entitled to approximately $0.3 million of tenant improvement allowances pursuant to the Sixth Amendment. In connection with the execution of the Sixth Amendment, the Company delivered to the lessor a letter of credit collateralized by restricted cash totaling $1.6 million. In total, at June 30, 2015, the Company leased approximately 143,000 square feet of office space pursuant to the lease agreement, as amended, which expires in June 2019. Lease commitments pursuant to the Sixth Amendment are approximately $6.1 million over the term of the lease. Future operating lease obligations as of June 30, 2015 are as follows: Years Ending December 31, Operating Leases Remainder of 2015 $ 4,569 2016 9,345 2017 9,544 2018 9,746 2019 5,065 2020 and thereafter   Total minimum lease payments $ 38,269 The Company is considered the  accounting owner  for a build-to-suit property and has recorded a build-to-suit lease obligation on its consolidated balance sheets. Additional information regarding the build-to-suit lease obligation is included in Note 8,  Build-To-Suit Lease Obligation.  Expected future lease payments under the build-to-suit lease as of June 30, 2015 are as follows: Years Ending December 31, Expected Cash Payments Under Build- To-Suit Lease Obligation Remainder of 2015 $ 1,177 2016 2,168 2017 2,233 2018 2,300 2019 2,368 2020 and thereafter 12,028 Total minimum lease payments $ 22,274 (b) Restricted Cash The Company had outstanding letters of credit collateralized by restricted cash totaling $13.3 million and $11.8 million at June 30, 2015 and December 31, 2014, respectively, to secure various operating leases. At June 30, 2015, $0.6 million and $12.7 million of restricted cash associated with these letter