Business Overview (Details)						1 Months Ended		3 Months Ended					9 Months Ended
	Sep. 01, 2017 USD ($) tranche	Feb. 28, 2017 USD ($)	Feb. 06, 2017 USD ($)	Jan. 31, 2017 $ / shares shares	Mar. 18, 2016 USD ($) $ / shares shares	Mar. 31, 2017 USD ($) shares	Nov. 30, 2016 USD ($) shares	Sep. 30, 2017 USD ($)	Mar. 31, 2017 USD ($) shares	Dec. 31, 2016 USD ($) shares	Sep. 30, 2016 USD ($)	Mar. 31, 2016 USD ($) shares	Sep. 30, 2017 USD ($) shares	Sep. 30, 2016 USD ($)	Dec. 31, 2015 USD ($)	Nov. 03, 2014 USD ($) $ / shares
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Net cash (used in) operating activities													$ (180,052,000)	$ (91,987,000)
Cash and cash equivalents								$ 117,787,000		$ 82,387,000	$ 109,090,000		117,787,000	109,090,000	$ 61,653,000
Net loss from operations								48,871,000			40,243,000		187,364,000	138,740,000
Working capital								110,500,000					110,500,000
Subsidiary, Sale of Stock [Line Items]
Proceeds of sale of common stock													121,951,000	89,845,000
Payment for indenture consent		$ 1,600,000
Debt conversion amount													4,912,000	82,274,000
Debt conversion expense								0	$ 1,209,000		$ 0		$ 1,209,000	$ 25,615,000
Common Shares
Subsidiary, Sale of Stock [Line Items]
Shares sold in private placement (in shares) | shares													20,325,204
Debt conversion expense (in shares) | shares									200,000				212,800
Convertible Senior Notes Due 2019
Subsidiary, Sale of Stock [Line Items]
Debt conversion amount					$ 79,800,000	$ 4,900,000	$ 55,700,000		$ 4,911,000
Number of shares issued on conversion of debt (in shares) | shares					35,300,000	1,800,000	20,500,000
Debt conversion per original conversion price (in shares) | shares						1,600,000				2,600,000		9,600,000
Conversion price (in dollars per share) | $ / shares					$ 3.11											$ 3.11
Aggregate principal amount								$ 18,600,000					$ 18,600,000			$ 200,000,000
Debt conversion expense										$ 14,500,000		$ 25,600,000
Public Stock Offering
Subsidiary, Sale of Stock [Line Items]
Shares sold in private placement (in shares) | shares				20,325,204
Shares issued (in dollars per share) | $ / shares				$ 6.15
Proceeds of sale of common stock			$ 121,600,000
CRG Servicing LLC | Secured Debt | Line of Credit | Term Loan
Subsidiary, Sale of Stock [Line Items]
Maximum borrowing capacity (up to)	$ 300,000,000.0
Proceeds from line of credit	100,000,000.0
Remaining borrowing capacity	$ 100,000,000.0
Interest rate per annum	9.50%
CRG Servicing LLC | Secured Debt | Line of Credit | Tranche One | Term Loan
Subsidiary, Sale of Stock [Line Items]
Remaining borrowing capacity	$ 50,000,000.0
Number of tranches | tranche	2
CRG Servicing LLC | Secured Debt | Line of Credit | Tranche Two | Term Loan
Subsidiary, Sale of Stock [Line Items]
Remaining borrowing capacity	$ 50,000,000.0
Number of tranches | tranche	2