Debt - Additional Information (Details) - USD ($)		3 Months Ended
	Dec. 12, 2018	Mar. 31, 2019	Dec. 31, 2018
Line Of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity		$ 40,000,000
Line of credit, available borrowing base		20,800,000
Line of credit, outstanding borrowings		0	$ 15,000,000
Loan and Security Agreement | Silicon Valley Bank | Revolving Credit Facility
Line Of Credit Facility [Line Items]
Line of credit, outstanding borrowings		0
Line of credit, stated interest rate	6.75%
Line of credit, frequency of periodic interest payment	monthly
Line of credit, term	2 years
Line of credit, commitment fee description	Upon entry into the Loan and Security Agreement (payable in installments and subject to certain conditions), and at the one year anniversary of the effective date of the Loan and Security Agreement (or, if earlier, upon termination of or an event of default under the Loan and Security Agreement), Keryx must pay to SVB a fee equal to 1.00% of the Line of Credit. Keryx is also required to pay on a quarterly basis a fee equal to 0.25% per annum of the average unused portion of the Line of Credit. Keryx must pay a termination fee of 2.00% of the Line of Credit, if the Loan and Security Agreement is terminated prior to the maturity date, subject to certain exceptions
Line of credit, commitment fee percentage	1.00%
Line of credit, frequency of commitment fee on unused portion	quarterly basis
Percentage of commitment fees percent on unused portion of credit facility	0.25%
Line of credit, termination fee percentage	2.00%
Covenant terms, description	The Loan and Security Agreement contains customary covenants applicable to Keryx and its subsidiaries, including maintaining insurance on its business, achievement of minimum revenue amounts, the incurrence of additional indebtedness, and future encumbrances on Keryx’s assets. In addition, the Keryx must maintain a liquidity ratio, defined as (i) the sum of unrestricted and unencumbered cash and cash equivalents maintained at SVB or its affiliates plus net billed accounts receivable divided by (ii) all outstanding obligations and liabilities of Keryx to SVB, including the aggregate amount of Keryx’s obligations to SVB under any business credit cards, of at least 1.5 to 1.0, measured monthly.
Minimum liquidity ratio	150.00%
Line of credit, debt default, description	Upon an event of default under the Loan and Security Agreement, SVB is entitled to accelerate and demand payment of all amounts outstanding under the Loan and Security Agreement, stop advancing money or extending credit to Keryx, demand that Keryx deposit at least 105% of the face amount of any letters of credit remaining undrawn to secure all obligations thereunder, and exercise other remedies available to SVB under the Loan and Security Agreement and at law or in equity.
Interest expense		$ 300,000
Amortization expense of origination and other fees	$ 0
Loan and Security Agreement | Minimum | Silicon Valley Bank | Revolving Credit Facility
Line Of Credit Facility [Line Items]
Line of credit, debt default, percentage	105.00%
Prime Rate | Loan and Security Agreement | Minimum | Silicon Valley Bank | Revolving Credit Facility
Line Of Credit Facility [Line Items]
Line of credit, variable interest rate	2.00%