Liability Related to Sale of Future Royalties - Summary of Liability Related to Potential Future Royalties (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended			34 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014
Other Liabilities Disclosure [Abstract]
Liability related to sale of future royalties-beginning balance	$ 128,520
Proceeds from sale of future royalties				124,000
Payments from Nektar to RPI	(7,000)			(10,000)
Non-cash CIMZIA® and MIRCERA®royalty revenue	(21,937)	(22,055)	(10,791)	(54,783)
Non-cash interest expense recognized	20,888	22,309	18,057	61,254
Liability related to sale of future royalties - ending balance	$ 120,471	$ 128,520		$ 120,471