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Intangible Assets and Goodwill - Additional Information (Details)		3 Months Ended		9 Months Ended
	Dec. 12, 2018	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) segment	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Finite-Lived Intangible Assets [Line Items]
Amortization expense		$ 9,000,000	$ 6,100,000	$ 27,032,000	$ 24,307,000
Goodwill		55,053,000		$ 55,053,000		$ 55,053,000
Number of operating segments \| segment				1
Goodwill impairment		$ 0	$ 0	$ 0	$ 0
Developed product rights for Auryxia
Finite-Lived Intangible Assets [Line Items]
Intangible assets, estimated useful life	6 years