Checkpoint Therapeutics, Inc. Quarterly report pursuant to Section 13 or 15(d)

Significant Accounting Policies - Additional Information (Details) - USD ($) $ in Millions		9 Months Ended	12 Months Ended
	Jan. 01, 2019	Sep. 30, 2019	Dec. 31, 2018	Mar. 17, 2015
Equity Method Investment, Annual Equity Fee, Percentage				2.50%
Fortress Biotech, Inc [Member]
Equity Method Investment, Annual Equity Fee, Percentage	2.50%
Stock Issued During Period, Shares, New Issues	960,428	55,750
Research and Development Expense [Member]
Stock Issued During Period, Value, Issued for Services			$ 1.7