Liability Related to the Sale of Future Royalties - Additional Information (Detail) - USD ($) $ in Thousands		1 Months Ended		3 Months Ended		12 Months Ended			70 Months Ended	82 Months Ended
	Feb. 24, 2012	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2018
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						$ 33,308	$ 30,531	$ 30,158		$ 170,839
Non-cash interest expense on liability related to sale of future royalties						$ 21,196	$ 18,869	$ 19,712		$ 141,649
Annual interest rate				18.70%	17.60%				17.00%
Prospective interest rate				29.00%	21.00%
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