INCOME TAXES (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($) item
Income Taxes
Accrued interest or penalties due to our net operating losses	$ 0	$ 0
Number of ownership changes | item			2
Deferred tax assets
Net operating loss carryforwards	417,000	392,000
Deferred revenues	1,000	1,000
Research and development tax credit carryforwards	53,000	53,000
Other	13,000	17,000
Total deferred tax assets	484,000	463,000
Valuation allowance	(484,000)	(463,000)
Net deferred tax assets	$ 0	$ 0
The differences between the U.S. federal statutory income tax rate to the Company's effective tax rate
U.S. federal income tax rate (as a percent)	35.00%	34.00%	35.00%
Non-deductible executive compensation (as a percent)	1.55%	(1.94%)	(0.16%)
Stock-based compensation (as a percent)	0.09%	(0.23%)	(1.11%)
Federal and state research credits (as a percent)	0.00%	0.00%	12.66%
Effect of Spin-Off Transaction (as a percent)	0.00%	0.00%	(203.20%)
Other (as a percent)	(0.29%)	(0.56%)	(4.04%)
Change in valuation allowance (as a percent)	(36.19%)	(31.27%)	160.85%
Effective tax rate (as a percent)	0.16%	0.00%	0.00%
Information related to valuation allowance
Increase (decrease) in valuation allowance	$ 20,600	$ 4,700	$ (103,800)
Gross unrecognized tax benefits
Gross unrecognized tax benefits at the beginning of the period	15,488	15,459	57,420
Gross decrease for tax positions for prior years			(42,650)
Gross increase in tax portions		29	689
Gross unrecognized tax benefits at the end of the period	15,488	$ 15,488	$ 15,459
Early adoption | ASU 2016-09
Information related to valuation allowance
Excess stock option tax benefits	46,900
Federal
Income Taxes
Net operating loss carryforwards	1,100
Federal | Research and development
Income Taxes
Tax credit carryforward amount	45,200
State
Income Taxes
Net operating loss carryforwards	674,300
State | Research and development
Income Taxes
Tax credit carryforward amount	$ 32,300