Condensed Consolidated Statements of Stockholders' Equity - USD ($)	Preferred Stock	Common Stock	Additional Paid-in Capital	Treasury Stock	Accumulated Other Comprehensive Loss	Accumulated Deficit	Total
Balance at Dec. 31, 2019	$ 0	$ 979,000	$ 606,686,000	$ (8,034,000)	$ (2,728,000)	$ (523,908,000)	$ 72,995,000
Balance (in shares) at Dec. 31, 2019	0	97,771,698
Issuance of common stock for options and warrants exercised		$ 27,000	3,825,000				3,852,000
Issuance of common stock for options and warrants exercised (in shares)		2,722,795
Repurchase of stock options to satisfy tax withholding obligations	$ 0	$ 0	(251,000)	0	0	0	(251,000)
Issuance of common stock pursuant to financing agreements		$ 4,000	1,395,000				1,399,000
Issuance of common stock pursuant to financing agreements (in shares)		434,336
Stock issuance costs	0	$ 0	(251,000)	0	0	0	(251,000)
Stock-based compensation expense, net of forfeitures	0	0	3,892,000	0	0	0	3,892,000
Foreign currency translation adjustment	0	0	0	0	(1,162,000)	0	(1,162,000)
Net loss attributable to CASI Pharmaceuticals, Inc.	0	0	(679,000)	0	0	(16,456,000)	(17,135,000)
Balance at Jun. 30, 2020	$ 0	$ 1,010,000	614,617,000	(8,034,000)	(3,890,000)	(540,364,000)	63,339,000
Balance (in shares) at Jun. 30, 2020	0	100,928,829
Balance at Mar. 31, 2020		$ 1,010,000	612,972,000	(8,034,000)	(3,554,000)	(532,032,000)	70,362,000
Balance (in shares) at Mar. 31, 2020		100,914,829
Issuance of common stock for options and warrants exercised			20,000				20,000
Issuance of common stock for options and warrants exercised (in shares)		14,000
Stock-based compensation expense, net of forfeitures			1,987,000				1,987,000
Foreign currency translation adjustment					(336,000)		(336,000)
Net loss attributable to CASI Pharmaceuticals, Inc.			(362,000)			(8,332,000)	(8,694,000)
Balance at Jun. 30, 2020	$ 0	$ 1,010,000	614,617,000	(8,034,000)	(3,890,000)	(540,364,000)	63,339,000
Balance (in shares) at Jun. 30, 2020	0	100,928,829
Balance at Dec. 31, 2020	$ 0	$ 1,240,000	658,246,000	(8,034,000)	589,000	(570,501,000)	81,540,000
Balance (in shares) at Dec. 31, 2020	0	123,943,829
Issuance of common stock pursuant to financing agreements		$ 159,000	32,341,000	0	0	0	32,500,000
Issuance of common stock pursuant to financing agreements (in shares)		15,853,658
Stock issuance costs			(2,019,000)	0	0	0	(2,019,000)
Stock-based compensation expense, net of forfeitures	$ 0	$ 0	3,038,000	0	0	0	3,038,000
Foreign currency translation adjustment	0	0	0	0	570,000	0	570,000
Net loss attributable to CASI Pharmaceuticals, Inc.	0	0	(1,067,000)	0	0	(19,762,000)	(20,829,000)
Balance at Jun. 30, 2021	$ 0	$ 1,399,000	690,539,000	(8,034,000)	1,159,000	(590,263,000)	94,800,000
Balance (in shares) at Jun. 30, 2021	0	139,797,487
Balance at Mar. 31, 2021		$ 1,399,000	690,018,000	(8,034,000)	485,000	(583,836,000)	100,032,000
Balance (in shares) at Mar. 31, 2021		139,797,487
Stock-based compensation expense, net of forfeitures			1,040,000				1,040,000
Foreign currency translation adjustment					674,000		674,000
Net loss attributable to CASI Pharmaceuticals, Inc.			(519,000)			(6,427,000)	(6,946,000)
Balance at Jun. 30, 2021	$ 0	$ 1,399,000	$ 690,539,000	$ (8,034,000)	$ 1,159,000	$ (590,263,000)	$ 94,800,000
Balance (in shares) at Jun. 30, 2021	0	139,797,487