Liabilities Related to the Sales of Future Royalties - Additional Information (Detail) - USD ($) $ in Thousands					1 Months Ended		12 Months Ended			106 Months Ended
	Dec. 31, 2020	Dec. 30, 2020	Dec. 16, 2020	Feb. 24, 2012	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2020
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							$ 48,563	$ 36,303	$ 33,308	$ 255,705
Non-cash interest expense on liability related to sale of future royalties							30,267	$ 25,044	$ 21,196	196,960
Purchase and Sale Agreement 2012
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
Non-cash royalty revenue							37,938			245,080
Non-cash interest expense on liability related to sale of future royalties							30,267			$ 196,960
Purchase and Sale Agreement 2020
Liability Related to the Sale of Future Royalties [Line Items]
Proceeds from sale of royalty rights		$ 150,000
Transaction costs related to sale of potential future royalties		$ 3,800
Non-cash royalty revenue	$ 10,625						10,625
Non-cash interest expense on liability related to sale of future royalties	$ 0						$ 0
Payment of transaction related to purchase and sale agreement			$ 210,000
Payment of transaction related to purchase and sale agreement if threshold is not achieved			240,000
Minimum transaction royalties payments needed to pay the difference between the 2025 threshold and 2020 transaction royalties			$ 208,000
Purchase and Sale Agreement with RPI
Liability Related to the Sale of Future Royalties [Line Items]
Payment made for milestone not achieved year two					$ 7,000
Payment made for milestone not achieved year one						$ 3,000