Debt - Deerfield Facility Agreement (Details) - USD ($)					1 Months Ended	12 Months Ended
	Sep. 01, 2016	Feb. 05, 2016	Nov. 21, 2014	Mar. 20, 2014	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Feb. 04, 2016	Mar. 17, 2014
Line of Credit Facility [Line Items]
Unamortized debt discount						$ 3,543,000	$ 5,642,000
Warrants converted to shares					268,614
Warrant conversion, value						1,074,000
Repayments under lines of credit						134,792,000	144,567,000	$ 156,106,000
Loss on debt extinguishment						$ (9,478,000)
Deerfield
Line of Credit Facility [Line Items]
Maximum borrowing capacity							$ 26,000,000			$ 50,000,000
Transaction fee as percentage of principal amount										2.50%
Line of credit			$ 6,000,000	$ 20,000,000
Net proceeds from initial draw under Facility Agreement			5,900,000	19,500,000
Unamortized debt discount			200,000	500,000
Remaining borrowing capacity			0
Debt instrument, stated interest rate									8.75%
Warrants converted to shares					268,614
Warrant conversion, value					$ 1,100,000
Repayments under lines of credit	$ 33,500,000
Repayments of lines of credit, principle and accrued interest	27,900,000
Repayments of lines of credit, prepayment of premium	5,600,000
Write off of unamortized expense	3,900,000
Loss on debt extinguishment	$ (9,500,000)
Deerfield | Initial warrants
Line of Credit Facility [Line Items]
Number of warrants issued (in shares)										520,833
Exercise price of warrants (dollars per share)										$ 16.68
Warrant amount reclassified as debt discount			$ 200,000	$ 2,300,000
Deerfield | Draw warrants
Line of Credit Facility [Line Items]
Maximum borrowing capacity										$ 50,000,000
Number of warrants issued (in shares)			100,000	333,333
Exercise price of warrants (dollars per share)			$ 16.68	$ 16.68
Line of credit				$ 20,000,000
Warrants value			$ 900,000	$ 4,700,000
Deerfield | Draw warrants | Maximum
Line of Credit Facility [Line Items]
Number of securities called by warrants associated with each disbursement borrowing (in shares)										833,333
Second amendment with Deerfield
Line of Credit Facility [Line Items]
Debt instrument, stated interest rate		14.75%
Portion of interest paid-in-kind, percentage	3.00%	6.00%
Amendment fee amount		$ 600,000
Amendment fee, installment amount		$ 200,000