Income (Loss) Per Common Share - Computation of Weighted Average Basic and Diluted Income (Loss) Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Earnings Per Share [Abstract]
Income (loss) from continuing operations	$ (63,600)	$ 11,400
Less: loss attributable to noncontrolling interest	(1,300)
Net income (loss) from continuing operations attributable to GlassBridge Enterprises, Inc.	(62,300)	11,400
Income from discontinued operations, net of income taxes		11,700
Net income	$ (63,600)	$ 23,100
Weighted average number of diluted shares outstanding during the period - basic and diluted	25,200	25,500
Continuing operations	$ (2,472.77)	$ 330.15
Discontinued operations		461.45
Net income	$ (2,472.77)	$ 791.60
Anti-dilutive shares excluded from calculation