Debt - Narrative (Details)			12 Months Ended
	Dec. 10, 2020 USD ($)	Nov. 11, 2019 USD ($) tranche	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Nov. 25, 2019 USD ($)
Line of Credit Facility [Line Items]
Term loan, net of facility fees, lender expenses and issuance costs			$ 97,543,000
Derivative liability			1,820,000	$ 2,420,000
Collateral Agent, Pharmakon
Line of Credit Facility [Line Items]
Derivative liability			1,800,000	2,400,000
BPCR Limited Partnership | Keryx | Term Loan | Collateral Agent, Pharmakon
Line of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity		$ 100,000,000
Line of credit, maximum borrowing capacity, number of available tranches | tranche		2
Debt instrument, term		5 years
Term loan, maturity term, potential reduction (up to)		1 year
Term loan, amortization period, potential reduction (up to)		1 year
Facility fee percentage on principal amount		2.00%
Facility fee paid, amount		$ 2,000,000
Prepayment premium percentage on principal if prepaid prior to third anniversary of funding		2.00%
Prepayment premium percentage on principal if prepaid prior to fourth anniversary and after third anniversary of funding		1.00%
Prepayment premium percentage on principal if prepaid after fourth anniversary of funding		0.50%
Interest expense			$ 10,900,000	$ 8,900,000
BPCR Limited Partnership | Keryx | Term Loan | Collateral Agent, Pharmakon | Debt Instrument, First Quarterly Periodic Payment, Period One
Line of Credit Facility [Line Items]
Term loan, first quarterly principal payment due in		33 months
BPCR Limited Partnership | Keryx | Term Loan | Collateral Agent, Pharmakon | Debt Instrument, First Quarterly Periodic Payment, Period Two
Line of Credit Facility [Line Items]
Term loan, first quarterly principal payment due in		48 months
BPCR Limited Partnership | Keryx | Term Loan | Collateral Agent, Pharmakon | Three-month LIBOR
Line of Credit Facility [Line Items]
Basis spread on floating interest rate		7.50%
BPCR Limited Partnership | Keryx | Term Loan | Collateral Agent, Pharmakon | LIBOR
Line of Credit Facility [Line Items]
Debt instrument, floor rate		2.00%
Debt instrument, cap rate		3.35%
BPCR Limited Partnership | Keryx | Term Loan | Collateral Agent, Pharmakon | Tranche A
Line of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity		$ 80,000,000
Term loan, net of facility fees, lender expenses and issuance costs					$ 77,300,000
BPCR Limited Partnership | Keryx | Term Loan | Collateral Agent, Pharmakon | Tranche B
Line of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity		$ 20,000,000
Proceeds from line of credit	$ 20,000,000