Liability Related to the Sale of Future Royalties - Additional Information (Detail) - USD ($) $ in Thousands		1 Months Ended		3 Months Ended
	Feb. 24, 2012	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2016	Mar. 31, 2015
Liability Related to the Sale of Future Royalties [Line Items]
Non-cash royalty revenue related to sale of future royalties				$ 6,535	$ 3,962
Non-cash interest expense on liability related to sale of future royalties				$ 5,045	$ 5,050
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 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