Debt (Details) $ / shares in Units, $ in Thousands		1 Months Ended			3 Months Ended		9 Months Ended		30 Months Ended
	Jan. 31, 2013 USD ($) item $ / shares $ / item shares	Nov. 30, 2016 USD ($)	May 31, 2016 USD ($)	Jan. 31, 2013 USD ($) item $ / shares $ / item	Sep. 30, 2016 USD ($) $ / shares $ / item	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) $ / shares $ / item	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) $ / shares $ / item	Dec. 31, 2015 USD ($)	Apr. 30, 2014 USD ($)
Debt disclosures
Total long-term debt					$ 735,849		$ 735,849		$ 735,849	$ 748,271
Unamortized debt issuance costs					(12,849)		(12,849)		(12,849)	(15,140)
Net long-term debt					719,449		719,449		719,449	733,131
Settlement amount for purchase of notes							8,095	$ 0
Amount received from capped call option							391	0
Interest amount added to principal balance							855	18,449
Long-acting beta agonist (LABA) collaboration | GSK
Debt disclosures
Royalty revenues					36,544	$ 16,796	99,662	$ 40,816
Convertible Subordinated Notes Due 2023
Debt disclosures
Convertible Subordinated Notes due 2023					$ 245,109		$ 245,109		$ 245,109	255,109
Total long-term debt			$ 9,800
Loan amount	$ 287,500		10,000	$ 287,500
Proceeds from issuances of note payable, net of debt issuance costs	$ 281,200
Conversion rate of shares				35.9903			50.5818
Conversion price of convertible notes into common stock (in dollars per share) | $ / shares	$ 27.79			$ 27.79	$ 19.77		$ 19.77		$ 19.77
Settlement amount for purchase of notes			8,100
Convertible Subordinated Notes Due 2023 | Other income (expense)
Debt disclosures
Gain on repurchase of notes			$ 1,700
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
Interest rate (as a percent)	2.125%			2.125%
Strike price for the underlying number of shares (in dollars per share) | $ / shares	$ 27.79						$ 19.77
Cap price for the underlying number of shares (in dollars per share) | $ / item	38.00			38.00	27.04		27.04		27.04
Amount received from capped call option							$ 400
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 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 above $38.00 per share
Debt disclosures
Incremental anti-dilutive benefit (in shares) | shares	0
9% fixed rate term notes due 2029
Debt disclosures
Non-recourse notes due 2029					$ 490,740		490,740		$ 490,740	493,162
Current portion of non-recourse notes due 2029					(3,551)		$ (3,551)		(3,551)	$ 0
Debt prepayment premium (as a percent)							2.50%
9% fixed rate term notes due 2029 | GSK
Debt disclosures
Loan amount					490,700		$ 490,700		490,700		$ 450,000
Interest rate (as a percent)											9.00%
Interest amount added to principal balance							$ 900		$ 44,000
Periodical interest payment					$ 3,300
9% fixed rate term notes due 2029 | Future | GSK
Debt disclosures
Periodical interest payment		$ 3,600