Income Taxes (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($) item	Dec. 31, 2013 USD ($)
Income Taxes
Income tax expenses	$ 0	$ 0	$ 0
Deferred tax assets:
Net operating loss carryforwards	392,000	386,000
Deferred revenues	1,000	2,000
Research and development tax credit carryforwards	53,000	53,000
Other	17,000	18,000
Total deferred tax assets	463,000	459,000
Valuation allowance	(463,000)	(459,000)
Net deferred tax assets	0	0
Information related to valuation allowance
Increase (decrease) in valuation allowance	$ 4,700	(103,800)	$ 70,100
Federal net operating losses		252,700
Valuation Allowance		88,600
Deferred tax assets		$ 9,200
The differences between the U.S. federal statutory income tax rate to the Company's effective tax rate
U.S. federal statutory income tax rate (as a percent)	34.00%	35.00%	34.00%
Non-deductible executive compensation (as a percent)	(1.94%)	(0.16%)	(0.07%)
Stock-based compensation (as a percent)	(0.23%)	(1.11%)	0.28%
Federal and state research credits (as a percent)	(0.00%)	12.66%	3.63%
Effect of Spin-Off Transaction (as a percent)	0.00%	(203.20%)	0.00%
Other (as a percent)	(0.56%)	(4.04%)	(2.51%)
Change in valuation allowance (as a percent)	(31.27%)	160.85%	(35.33%)
Effective tax rate (as a percent)	0.00%	0.00%	0.00%
Gross unrecognized tax benefits
Gross unrecognized tax benefits at the beginning of the period	$ 15,459	$ 57,420	$ 52,500
Gross decrease for tax positions for prior years		(42,650)	(565)
Gross increase in tax positions for current year	29	689	5,485
Gross unrecognized tax benefits at the end of the period	15,488	15,459	$ 57,420
Accrued interest or penalties due to our net operating losses	0	$ 0
Number of ownership changes | item		2
Federal
Operating Loss and Tax Credit Carryforward
Net operating loss carryforwards	1,174,700
Federal | Research and Development
Operating Loss and Tax Credit Carryforward
Tax credit carryforward amount	45,200
State
Operating Loss and Tax Credit Carryforward
Net operating loss carryforwards	676,500
State | Research
Operating Loss and Tax Credit Carryforward
Tax credit carryforward amount	$ 32,300