Income Taxes Income Taxes - Schedule of Deferred Income Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets:
Net operating loss carryforwards	$ 57,327	$ 57,177
Stock—based compensation	2,863	6,706
Development costs	26,805	20,101
Other	1,939	2,108
Net deferred tax assets	88,934	86,092
Valuation allowance	(88,934)	(86,092)
Deferred tax assets, net	$ 0	$ 0