Convertible Senior Subordinated Notes due 2015 (Details) (USD $)	9 Months Ended			1 Months Ended	9 Months Ended
	Sep. 30, 2010	Sep. 30, 2011	Dec. 31, 2010	Sep. 30, 2010 2015 Notes days	Sep. 30, 2011 2015 Notes years	Sep. 28, 2010 2015 Notes
Convertible Senior Subordinated Notes and Collaborator Loan
Convertible senior subordinated notes (due 2015)		$ 400,000,000	$ 400,000,000	$ 400,000,000	$ 400,000,000
Interest rate (as a percent)				3.35%	3.35%
Net proceeds from convertible debt offering	391,645,000			391,600,000
Underwriting discount				8,000,000
Debt issuance costs				400,000
Conversion price (in dollars per share)						$ 48.83
Original conversion rate, number of shares to be issued per $1000 of principal (in shares)				20.4794
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