Checkpoint Therapeutics, Inc. Annual report pursuant to Section 13 and 15(d)

Significant Accounting Policies - Additional Information (Details) - USD ($) $ in Millions				12 Months Ended
	Jan. 01, 2021	Jan. 01, 2020	Mar. 17, 2015	Dec. 31, 2020	Dec. 31, 2019
Equity Method Investment, Annual Equity Fee, Percentage			2.50%
Fortress Biotech, Inc [Member]
Equity Method Investment, Annual Equity Fee, Percentage	2.50%	2.50%		2.50%
Stock Issued During Period, Shares, New Issues	1,742,449	1,459,305		310,625	441,816
Research and development [Member]
Stock Issued During Period, Value, Issued for Services				$ 4.6	$ 2.5