Income (Loss) per Common Share - Computation of Weighted Average Basic and Diluted Income (Loss) per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Numerator:
Loss from continuing operations	$ (22.9)	$ (39.8)
Less: loss attributable to noncontrolling interest	(10.2)	0.0
Net loss from continuing operations attributable to GlassBridge Enterprises, Inc.	(12.7)	(39.8)
Income (loss) from discontinued operations	4.3	(85.4)
Net loss attributable to GlassBridge Enterprises, Inc.	$ (8.4)	$ (125.2)
Denominator:
Weighted average number of common shares outstanding during the period	4.7	3.7
Dilutive effect of stock-based compensation plans	0.0	0.0
Weighted average number of diluted shares outstanding during the period	4.7	3.7
Income (loss) per common share attributable to GlassBridge common shareholders — basic and diluted:
Continuing operations (in dollars per share)	$ (2.70)	$ (10.76)
Discontinued operations (in dollars per share)	0.91	(23.08)
Net loss (in dollars per share)	$ (1.79)	$ (33.84)
Anti-dilutive shares excluded from calculation (in shares)	0.3	0.4