Accounting Policies (Details 2) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Collaborative Arrangements
Collaborative revenues	$ 29,879,000	$ 24,360,000	$ 97,480,000	$ 40,382,000
Research and development expense associated with collaborative programs	40,000,000	40,000,000	64,000,000	77,000,000
Period prior to the labeled expiration date in which distributors have right to return unopened, unprescribed INCIVEK (teleprevir) (in months)			6
Period after the labeled expiration date in which distributors have right to return unopened, unprescribed INCIVEK (teleprevir) (in months)			12
Expiration period of INCIVEK (telaprevir) (in years)			2
Discount rate for payments made within 30 days (as a percent)			2.00%
Janssen Pharmaceutical, N.V.
Collaborative Arrangements
Collaborative revenues	9,058,000	11,882,000	65,174,000	18,346,000
Mitsubishi Tanabe Pharma Corporation
Collaborative Arrangements
Collaborative revenues	$ 14,873,000	$ 12,036,000	$ 26,358,000	$ 21,594,000