Business Combination - Additional Information (Details)		3 Months Ended
	Dec. 12, 2018 USD ($)	Mar. 31, 2020 USD ($) shares
Business Acquisition [Line Items]
Total fair value consideration		$ 527,754,000
Intangible assets, estimated useful life		9 years
Keryx Biopharmaceuticals, Inc.
Business Acquisition [Line Items]
Total fair value consideration	$ 527,754,000
Business combination, Purchase price	$ 527,754,000
Risk-adjusted discount rate used to calculate present value of future expected cash inflows of intangible assets	20.00%
Preliminary fair value of the off-market element	$ 29,510,000
Goodwill deductible for tax purposes	$ 0
Deferred tax liabilities		$ 35,100,000
Keryx Biopharmaceuticals, Inc. | Auryxia
Business Acquisition [Line Items]
Intangible assets, estimated useful life	9 years
Keryx Biopharmaceuticals, Inc. | Common Stock
Business Acquisition [Line Items]
Total fair value consideration	$ 516,492,000
Keryx Biopharmaceuticals, Inc. | Merger Agreement
Business Acquisition [Line Items]
Outstanding common stock and awards converted into right to receive shares and awards, ratio	0.37433	0.37433
Total fair value consideration	$ 527,800,000
Additional shares expected to be issued | shares		4,000,000
Aggregate shares available for conversion | shares		39,600,000
Fair value of additional shares issued		$ 13,400,000
Keryx Biopharmaceuticals, Inc. | Notes Conversion Agreement
Business Acquisition [Line Items]
Convertible notes amount		$ 164,700,000
Keryx Biopharmaceuticals, Inc. | Notes Conversion Agreement | Common Stock
Business Acquisition [Line Items]
Convertible notes converted into shares | shares		35,582,335