Condensed Consolidated Statements of Operations (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Statement [Abstract]
Net revenue		$ 0.4		$ 0.7
Operating expenses:
Selling, general and administrative	3.3	3.0	6.2	7.1
Restructuring and other			0.3
Total operating expenses	3.3	3.0	6.5	7.1
Operating loss	(3.3)	(2.6)	(6.5)	(6.4)
Other income (expense):
Interest expense	(0.2)	(0.7)	(1.9)	(1.8)
Realized loss on investments		(0.1)	(0.2)	(1.8)
Gain on Chapter 11 reorganization (See Note 6 – Debt)			13.8
Bank Loan forgiveness (See Note 6 – Debt)			0.4
Defined benefit plan adjustment				(8.5)
Other income (expense), net	0.4	(0.1)	0.4
Total other income (expense)	0.2	(0.9)	12.5	(12.1)
Income (loss) from operations before income taxes	(3.1)	(3.5)	6.0	(18.5)
Income (loss) from operations	(3.1)	(3.5)	6.0	(18.5)
Net income (loss)	(3.1)	(3.5)	6.0	(18.5)
Less: Net loss attributable to noncontrolling interest	(0.3)	(0.2)	(0.7)	(0.9)
Net income (loss) attributable to GlassBridge Enterprises, Inc.	$ (2.8)	$ (3.3)	$ 6.7	$ (17.6)
Income (loss) per common share attributable to GlassBridge Enterprises, Inc. common shareholders — basic and diluted:
Net income (loss)	$ (111.11)	$ (131.13)	$ 265.87	$ (698.19)
Weighted average common shares outstanding:
Basic and diluted (thousands)	25.2	25.2	25.2	25.2