Long-Term Debt (Details) $ / shares in Units, $ in Thousands			1 Months Ended	12 Months Ended				16 Months Ended	21 Months Ended
	Jul. 15, 2014 $ / shares shares	Jun. 01, 2014 $ / shares $ / item	Jan. 31, 2013 USD ($) item $ / shares $ / item shares	Apr. 17, 2017	Dec. 31, 2015 USD ($) $ / shares $ / item	Dec. 31, 2014 USD ($) shares	Dec. 31, 2013 USD ($) shares	Apr. 17, 2016	Dec. 31, 2015 USD ($) $ / shares $ / item	Apr. 30, 2014 USD ($)
Debt disclosures
Convertible Subordinated Notes due 2023					$ 255,109	$ 255,109			$ 255,109
Non-Recourse Notes Payable due 2029					493,162	470,527			493,162
Total long term debt					748,271	725,636			748,271
Proceeds from issuances of note payable, net of debt issuance costs					0	434,677	$ 281,622
Interest amount added to principal balance					22,635	$ 20,527	$ 0
Common Stock
Debt disclosures
Number of common shares issued upon debt conversion | shares						1,520,000	6,668,000
Convertible Subordinated Notes Due 2023
Debt disclosures
Convertible Subordinated Notes due 2023					$ 255,109	$ 255,109			$ 255,109
Loan amount			$ 287,500
Proceeds from issuances of note payable, net of debt issuance costs			$ 281,200
Interest rate (as a percent)					2.125%				2.125%
Conversion rate of shares		0.0469087	0.0359903		0.0505818
Conversion price of convertible notes into common stock (in dollars per share) | $ / shares		$ 21.32	$ 27.79		$ 19.77				$ 19.77
Percentage of principal amount at which the entity may be forced to redeem some or all notes as a result of a fundamental change (as defined)			100.00%
Convertible Subordinated Notes Due 2023 | Common Stock
Debt disclosures
Conversion price of convertible notes into common stock (in dollars per share) | $ / shares	$ 21.32
Number of common shares issued upon debt conversion | shares	1,519,402
Number of common stares received | shares	149,645
Convertible Subordinated Notes Due 2023 | Privately-negotiated capped call option
Debt disclosures
Payments for capped call options			$ 36,800
Number of derivative instruments purchased | item			2
Strike price for the underlying number of shares (in dollars per share) | $ / shares		$ 21.32	$ 27.79		$ 19.77
Cap price for the underlying number of shares (in dollars per share) | $ / item		29.16	38.00		27.04				27.04
Convertible Subordinated Notes Due 2023 | Stock prices below $27.79 per share | Maximum
Debt disclosures
Net shares settlement payable to the entity | shares			2,779,659
Convertible Subordinated Notes Due 2023 | Stock prices below $27.79 per share | Minimum
Debt disclosures
Net shares settlement payable to the entity | shares			0
9% fixed rate term notes due 2029
Debt disclosures
Non-Recourse Notes Payable due 2029					$ 493,162	470,527			$ 493,162
Loan amount										$ 450,000
Interest rate (as a percent)										9.00%
Interest amount added to principal balance					$ 22,700	$ 20,500			$ 43,200
Debt issuance costs										$ 15,300
9% fixed rate term notes due 2029 | GSK
Debt disclosures
Percentage of royalties from global net sales to secure debt										40.00%
9% fixed rate term notes due 2029 | Future
Debt disclosures
Debt prepayment premium (as a percent)				2.50%				5.00%