Notes Payable (Details) (USD $)			1 Months Ended								1 Months Ended
	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2014 Convertible Subordinated Notes Due 2023	Jan. 31, 2013 Convertible Subordinated Notes Due 2023	Jun. 30, 2014 Convertible Subordinated Notes Due 2023 Privately-negotiated capped call option	Jan. 31, 2013 Convertible Subordinated Notes Due 2023 Privately-negotiated capped call option Item	Jan. 31, 2013 Convertible Subordinated Notes Due 2023 Stock prices below $27.79 per share Maximum	Jan. 31, 2013 Convertible Subordinated Notes Due 2023 Stock prices below $27.79 per share Minimum	Jan. 31, 2013 Convertible Subordinated Notes Due 2023 Stock prices above $38.00 per share	Jun. 30, 2014 9% fixed rate term notes due 2029	Apr. 30, 2014 9% fixed rate term notes due 2029 GSK	Jun. 30, 2014 9% fixed rate term notes due 2029 GSK
Debt disclosures
Loan amount				$ 287,500,000							$ 450,000,000
Proceeds from issuance of debt, net of issuance costs				281,200,000							434,700,000
Payments on capped call option transactions						36,800,000
Number of derivative instruments purchased						2
Interest rate (as a percent)			2.125%								9.00%
conversion rate of shares			0.0469087	0.0359903
Conversion price of convertible notes into common stock (in dollars per share)			$ 21.32	$ 27.79
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%
Strike price for the underlying number of shares (in dollars per share)					$ 21.32	$ 27.79
Cap price for the underlying number of shares (in dollars per share)					$ 29.16	$ 38.00
Net shares settlement payable to the entity							2,779,659	0
Incremental anti-dilutive benefit (in shares)									0
Percentage of royalties from global net sales											40.00%
Balance of segregated bank account classified as current restricted cash	14,232,000	0									200,000
Reserve account established to cover a portion of the remaining milestone payments											32,000,000	14,000,000
Reserve account for covering remaining milestone payments as a percentage of future milestone payments											40.00%
Transaction costs											15,300,000
Future minimum principal payments
Six months remaining in 2014										0
2015										0
2016										10,831,000
2017										52,935,000
2018										101,779,000
Thereafter										337,964,000
Total payments										$ 503,509,000