Condensed Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Statement [Abstract]
Net revenue	$ 0.0	$ 0.0	$ 0.0	$ 0.0
Cost of goods sold	0.0	0.0	0.0	0.0
Gross profit	0.0	0.0	0.0	0.0
Operating expenses:
Selling, general and administrative	1.9	2.3	5.1	7.0
Research and development	0.0	0.0	0.0	0.0
GBAM Fund expenses	0.1	0.3	0.3	0.3
Restructuring and other	0.0	0.1	0.1	0.0
Total operating expenses	2.0	2.7	5.5	7.3
Operating loss from continuing operations	(2.0)	(2.7)	(5.5)	(7.3)
Other income (expense):
Interest expense	0.0	0.0	(0.1)	0.0
Net gain (loss) from GBAM Fund activities	(0.2)	1.0	(0.7)	1.0
Other income (expense), net	0.1	0.1	0.4	(0.6)
Total other income (expense)	(0.1)	1.1	(0.4)	0.4
Loss from continuing operations before income taxes	(2.1)	(1.6)	(5.9)	(6.9)
Income tax benefit	0.0	3.5	0.0	3.5
Gain (loss) from continuing operations	(2.1)	1.9	(5.9)	(3.4)
Discontinued operations:
Gain on sale of discontinued businesses, net of income taxes	6.1	0.0	6.1	0.0
Gain (loss) from discontinued operations, net of income taxes	2.9	6.1	3.7	(1.5)
Gain (loss) from discontinued operations, net of income taxes	9.0	6.1	9.8	(1.5)
Net gain (loss)	$ 6.9	$ 8.0	$ 3.9	$ (4.9)
Gain (loss) per common share attributable to GlassBridge common shareholders — basic and diluted:
Continuing operations (in dollars per share)	$ (0.40)	$ 0.38	$ (1.16)	$ (0.74)
Discontinued operations (in dollars per share)	1.73	1.22	1.92	(0.33)
Net gain (loss) (in dollars per share)	$ 1.33	$ 1.60	$ 0.76	$ (1.07)
Weighted average common shares outstanding:
Basic and diluted (in shares)	5.2	5.0	5.1	4.6