INCOME TAXES (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income tax benefit (provision):
Federal									$ 30,962	$ 19,394	$ 16,204
State									4,920	4,237	3,131
Foreign											84
Expiration of Net Operating Losses and Research & Development Tax Credits									(126)	(1,426)	(411)
Income tax benefit (provision) before valuation allowance									35,756	22,205	19,008
Deferred tax valuation allowance									(35,756)	(22,205)	(19,008)
Income tax benefit (provision)									0
Reconciliation between the amount of reported income tax and the amount computed using U.S. Statutory rate
U.S. Statutory rate (as a percent)									34.00%
Pre-tax loss	(22,062)	(23,140)	(19,016)	(17,332)	(16,807)	(15,027)	(13,773)	(13,516)	(81,550)	(59,123)	(44,799)
Loss at Statutory Rates									(27,727)	(20,102)	(15,213)
Research and Development Credits									(3,261)		(1,736)
State Taxes									(4,920)	(4,237)	(3,131)
Other									26	708	661
Expiration of Net Operating Losses and Research & Development Tax Credits									126	1,426	411
Change in Valuation Allowance									35,756	22,205	19,008
Income tax benefit (provision)									0
Gross Deferred Tax Assets
Net Operating Loss Carryforwards	79,558				67,728				79,558	67,728
Tax Credit Carryforwards	25,582				20,692				25,582	20,692
Deferred Expenses	61,370				43,226				61,370	43,226
Stock-based Compensation	3,926				3,264				3,926	3,264
Fixed Assets	1,638				2,156				1,638	2,156
Accrued Expenses and Other	623				241				623	241
Gross Deferred Tax Assets	172,697				137,307				172,697	137,307
Gross Deferred Tax Liabilities
Other Acquired Intangibles	(4,115)				(4,481)				(4,115)	(4,481)
IPR&D Intangibles	(4,661)				(4,661)				(4,661)	(4,661)
Gross Deferred Tax Liabilities	(8,776)				(9,142)				(8,776)	(9,142)
Total Deferred Tax Assets and Liabilities	163,921				128,165				163,921	128,165
Deferred Tax Assets Valuation Allowance	(168,582)				(132,826)				(168,582)	(132,826)
Net Deferred Tax Asset (Liability)	$ (4,661)				$ (4,661)				$ (4,661)	$ (4,661)