Liability Related to Sale of Future Royalties - Additional Information (Detail) - USD ($) $ in Thousands		1 Months Ended		3 Months Ended		9 Months Ended
	Feb. 24, 2012	Mar. 31, 2014	Mar. 31, 2013	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Liability Related to Sale of Future Royalties [Line Items]
Non-cash royalty revenue related to sale of future royalties				$ 6,050	$ 6,143	$ 14,752	$ 16,753
Annual interest rate						17.00%
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.
Purchase and Sale Agreement with RPI [Member]
Liability Related to Sale of Future Royalties [Line Items]
Proceeds from sale of royalty rights	$ 124,000
Payment made for milestone not achieved year one			$ 3,000
Payment made for milestone not achieved year two		$ 7,000