Subsequent Events (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Subsequent Event [Line Items]
Royalty revenue by product line	$ 3,095,000	$ 2,545,000	$ 2,367,000	$ 2,319,000	$ 1,999,000	$ 1,745,000	$ 1,756,000	$ 1,756,000	$ 10,327,000	$ 7,255,000	$ 5,172,000
Outstanding convertible subordinated notes, due date									February 28, 2012
Potential future payments for development milestones									179,300,000
Subsequent Events (Textual) [Abstract]
Outstanding convertible subordinated notes	214,955,000								214,955,000
Outstanding convertible subordinated notes, interest rate	3.25%								3.25%
Purchase and Sale Agreement with RPI [Member]
Subsequent Event [Line Items]
Proceeds from sale of royalty rights									124,000,000
Structuring Transaction Costs									4,500,000
Effective interest rate under Purchase and Sale agreement									17.00%
Scenario One [Member] | Purchase and Sale Agreement with RPI [Member]
Subsequent Event [Line Items]
Contingent considerations, potential cash payments	3,000,000								3,000,000
Contingent considerations, description									(a) $3.0 million if certain worldwide net sales thresholds of MIRCERA® for the 12 month period ending on December 31, 2012 are not achieved
Scenario Two [Member] | Purchase and Sale Agreement with RPI [Member]
Subsequent Event [Line Items]
Contingent considerations, description									(b) up to an additional $7.0 million if certain worldwide net sales thresholds of MIRCERA® for the 12 month period ending on December 31, 2013 are not achieved
Maximum [Member] | Scenario Two [Member] | Purchase and Sale Agreement with RPI [Member]
Subsequent Event [Line Items]
Contingent considerations, potential cash payments	7,000,000								7,000,000
Net sales from MIRCERA and CIMZIA [Member]
Subsequent Event [Line Items]
Royalty revenue by product line									8,300,000	5,400,000	2,700,000
Roche [Member]
Subsequent Event [Line Items]
Received upfront payment									5,000,000
Potential future payments for development milestones									$ 22,000,000