Net Loss Per Share - Basic and diluted net loss per share computation (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2022	Sep. 30, 2021
Numerator:
Net loss attributable to CASI Pharmaceuticals, Inc.	$ (5,201)	$ (7,680)	$ (8,596)	$ (10,224)	$ (6,946)	$ (13,883)	$ (21,477)	$ (31,053)
Denominator:
Weighted average number of common stock	13,606,130			13,979,636			13,668,553	13,486,024
Denominator for basic and diluted net loss per share calculation	13,606,130			13,979,636			13,668,553	13,486,024
Net loss per share (basic)	$ (0.38)			$ (0.73)			$ (1.57)	$ (2.30)
Net loss per share (diluted)	$ (0.38)			$ (0.73)			$ (1.57)	$ (2.30)