8. Commitments and Contingencies Operating Leases and Subleases We lease approximately 150,000 square feet of office and laboratory space in two buildings in South San Francisco, California, under a non-cancelable operating lease that ends in May 2020. We may extend the terms of this lease for two additional five-year periods. Future minimum lease payments under this lease, exclusive of executory costs, at December 31, 2014, were as follows: (In thousands) Years ending December 31: 2015 $ 5,770 2016 5,943 2017 6,121 2018 6,305 2019 6,494 Thereafter 2,758 ? ? ? ? ? Total $ 33,391 ? ? ? ? ? ? ? ? ? ? Expenses and income associated with operating leases were as follows: Year Ended December 31, (In thousands) 2014 2013 2012 Rent expense $ 6,616 $ 5,763 $ 5,469 Sublease income, net $   $   $ (160 ) Special Long-Term Retention and Incentive Cash Awards Program In 2011, Theravance granted special long-term retention and incentive cash bonus awards to certain employees. The awards had dual triggers of vesting based upon the achievement of certain performance conditions over a six-year timeframe from 2011 through December 31, 2016 and continued employment. In May 2014, Theravance's Compensation Committee determined that the requisite performance conditions for the first tranche of the awards were achieved and, as a result, we recognized cash bonus expense of $9.5 million during the nine months ended September 30, 2014. In May 2014, the total cash bonus of $9.5 million for the first tranche was paid. In May 2014, Theravance's Compensation Committee approved the modification of the remaining tranches related to these awards contingent upon the Spin-Off. The modification acknowledged the Spin-Off and permitted recognition of achievement of the original performance conditions that were met prior to the Spin-Off, triggering a 12-month service-based vesting for a portion of the cash awards. The maximum amount payable by us under these modified cash bonus awards is $10.4 million. The remaining tranches of the cash awards were fo