Liability Related to Sale of Future Royalties (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012
Summary of liability related to potential future royalties
Beginning balance
Proceeds from sale of potential future royalties	124,000
Non-cash interest expense	1,785
MIRCERA and CIMZIA royalties remitted to RPI
Ending balance	$ 125,785