Income (Loss) per Common Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Numerator:
Loss from continuing operations	$ (2.3)	$ (5.9)	$ (3.6)	$ (13.2)
Less: loss attributable to noncontrolling interest	(0.3)	(2.0)	(0.3)	(3.5)
Net loss from continuing operations attributable to GlassBridge Enterprises, Inc.	(2.0)	(3.9)	(3.3)	(9.7)
Income (loss) from discontinued operations, net of income taxes	0.7	(1.2)	0.3	(3.2)
Net loss attributable to GlassBridge Enterprises, Inc.	$ (1.3)	$ (5.1)	$ (3.0)	$ (12.9)
Denominator:
Weighted average number of common shares outstanding during the period - basic and diluted (in shares)	5.1	5.0	5.1	4.5
Income (loss) per common share attributable to GlassBridge common shareholders — basic and diluted:
Continuing operations (in dollars per share)	$ (0.39)	$ (0.78)	$ (0.65)	$ (2.16)
Discontinued operations (in dollars per share)	0.14	(0.24)	0.06	(0.71)
Net loss (in dollars per share)	$ (0.25)	$ (1.02)	$ (0.59)	$ (2.87)
Anti-dilutive shares excluded from calculation (in shares)	0.4	0.3	0.3	0.3