Basis of Presentation, Accounting Policies and Going Concern (Details) - USD ($)		12 Months Ended
	Jan. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Mar. 01, 2017	Nov. 03, 2014	Dec. 31, 2013
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash and cash equivalents		$ 82,387,000	$ 61,653,000	$ 146,470,000			$ 18,130,000
Cash, cash equivalents, and available for sale securities		111,800,000
Net cash provided by (used in) operating activities		(129,800,000)	(101,000,000)
Working capital		59,500,000	95,500,000
Available-for-sale securities		0	50,097,000
Property, Plant and Equipment [Line Items]
Prepaid research and development costs		$ 500,000	$ 3,100,000
Total shares issuable upon exercise or conversion (in shares)		36,347,633	76,809,137	86,522,903
Stock Options
Property, Plant and Equipment [Line Items]
Total shares issuable upon exercise or conversion (in shares)		27,867,171	20,953,375	16,567,020
Warrants
Property, Plant and Equipment [Line Items]
Total shares issuable upon exercise or conversion (in shares)		919,690	4,726,823	5,647,203
Senior Convertible Notes
Property, Plant and Equipment [Line Items]
Total shares issuable upon exercise or conversion (in shares)		7,560,772	51,128,939	64,308,680
Convertible Senior Notes Due 2019
Property, Plant and Equipment [Line Items]
Aggregate principal amount		$ 23,500,000	$ 159,000,000	$ 200,000,000		$ 200,000,000
Number of shares issued on conversion of debt (in shares)		7,560,772	51,128,939	64,308,680
Minimum | Furniture and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life		2 years
Maximum | Furniture and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life		5 years
Subsequent Event | Convertible Senior Notes Due 2019
Property, Plant and Equipment [Line Items]
Aggregate principal amount					$ 19,500,000
Public stock offering | Subsequent Event
Property, Plant and Equipment [Line Items]
Number of shares issued/sold in transaction	20,325,204
Public offering price (in dollars per share)	$ 6.15
Proceeds yielded from offering	$ 121,600,000