Common Stock and Convertible Senior Subordinated Notes (Details 2) (USD $)	12 Months Ended				1 Months Ended	12 Months Ended		1 Months Ended	12 Months Ended		3 Months Ended
	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008	Dec. 31, 2011	Sep. 30, 2010 Convertible Senior Subordinated Notes 3.35 Percent Due 2015 D Y	Dec. 31, 2011 Convertible Senior Subordinated Notes 3.35 Percent Due 2015	Sep. 29, 2010 Convertible Senior Subordinated Notes 3.35 Percent Due 2015	Jan. 31, 2009 Convertible Senior Subordinated Notes (due 2013)	Dec. 31, 2009 Convertible Senior Subordinated Notes (due 2013)	Jan. 02, 2009 Convertible Senior Subordinated Notes (due 2013)	Mar. 31, 2010 Convertible Senior Subordinated Notes (due 2013) First quarter 2010 conversion
Convertible Senior Subordinated Notes and Collaborator Loan
Convertible senior subordinated notes	$ 400,000,000			$ 400,000,000	$ 400,000,000	$ 400,000,000	$ 400,000,000			$ 287,500,000	$ 32,100,000
Interest rate (as a percent)						3.35%		4.75%
Net proceeds from convertible debt offering	391,645,000		278,607,000		391,600,000
Underwriting discount					8,000,000
Debt issuance costs					400,000
Conversion price (in dollars per share)							$ 48.83			$ 23.14
Original conversion rate, number of shares to be issued per $1000 of principal (in shares)					20.4794			43.22
Convertible debt principal amount, basis for exchange					1,000
Percent closing price needs to exceed the conversion price for at least 20 trading days within 30 consecutive trading days for provisional redemption (as a percent)					130.00%
Minimum number of days within 30 consecutive trading days the closing price needs to exceed the conversion price for provisional redemption (in days)					20
Total consecutive trading days during which the closing price must exceed the conversion price for at least 20 trading days for provisional redemption (in days)					30
Percentage of principal amount used in computation of provisional redemption price (as a percent)					100.00%
Total interest payments on notes being provisionally redeemed equal to interest for specified number of years (in years)					3
Convertible subordinated notes exchanged or converted									255,400,000
Non-cash expense on exchange of convertible subordinated notes		(18,137,000)							18,100,000
Convertible subordinated notes exchanged or converted (in shares)									11,581,838		1,386,006
Accrued interest offset to additional paid-in capital on conversion/exchange of convertible senior subordinated notes (due 2013)	140,000	3,355,000							3,400,000		100,000
Unamortized debt issuance costs of converted/exchanged convertible senior subordinated notes (due 2013) offset to additional paid-in capital	$ 624,000	$ 5,899,000							$ 5,900,000		$ 600,000