Liability Related to the Sale of Future Royalties - Additional Information (Detail) - USD ($) $ in Thousands		1 Months Ended		12 Months Ended			46 Months Ended
	Feb. 24, 2012	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2015
Liability Related to the Sale of Future Royalties [Line Items]
Royalty agreement contingent payment description				As a result of worldwide net sales of MIRCERA® for the 12 month periods ended December 31, 2013 and 2012 not reaching certain minimum thresholds.
Non-cash royalty revenue related to sale of future royalties				$ 22,058	$ 21,937	$ 22,055	$ 76,841
Non-cash interest expense on liability related to sale of future royalties				$ 20,619	$ 20,888	$ 22,309	$ 81,873
Annual interest rate				17.00%
Purchase and Sale Agreement with RPI [Member]
Liability Related to the Sale of Future Royalties [Line Items]
Proceeds from sale of royalty rights	$ 124,000
Transaction costs related to sale of potential future royalties	$ 4,400
Payment made for milestone not achieved year two		$ 7,000
Payment made for milestone not achieved year one			$ 3,000