Income Taxes (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets:
Net operating loss carryforwards	$ 87,267	$ 91,365
Research credit carryforwards	14,322	13,884
Other, net	2,637	3,417
Deferred revenue	0	0
Total deferred tax assets	104,226	108,666
Valuation allowance	(104,226)	(108,666)
Net deferred tax assets	$ 0	$ 0