Long-Term Debt (Details) $ / shares in Units, $ in Thousands				1 Months Ended	3 Months Ended		18 Months Ended	37 Months Ended
	Jul. 15, 2014 $ / shares shares	Jun. 30, 2014 $ / shares $ / item	Jan. 31, 2013 USD ($) item $ / shares $ / item shares	Jan. 31, 2013 USD ($) item $ / shares $ / item	Mar. 31, 2016 USD ($) $ / shares $ / item	Mar. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Apr. 17, 2017	Dec. 31, 2015 USD ($)	Apr. 30, 2014 USD ($)
Debt disclosures
Total long-term debt					$ 748,954				$ 748,271
Less: unamortized debt issuance costs					14,441				15,140
Net long-term debt					734,513				733,131
Interest amount added to principal balance					683	$ 6,427
Convertible Subordinated Notes Due 2023
Debt disclosures
Convertible Subordinated Notes due 2023					$ 255,109				255,109
Loan amount			$ 287,500	$ 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		46.9087		35.9903	50.5818
Conversion price of convertible notes into common stock (in dollars per share) | $ / shares		$ 21.32	$ 27.79	$ 27.79	$ 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
Debt Conversion, Converted Instrument, Shares Issued | 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	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	38.00	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
Convertible Subordinated Notes Due 2023 | Stock prices above $38.00 per share
Debt disclosures
Incremental Common Shares Attributable to Capped Call Options | shares			0
9% fixed rate term notes due 2029
Debt disclosures
Non-Recourse Notes Payable due 2029					$ 493,845				$ 493,162
9% fixed rate term notes due 2029 | GSK
Debt disclosures
Loan amount										$ 450,000
Interest rate (as a percent)										9.00%
Interest amount added to principal balance					$ 700	$ 6,400	$ 43,800
9% fixed rate term notes due 2029 | Future
Debt disclosures
Debt prepayment premium (as a percent)								2.50%