Operating Segment and Related Information - Operating Segments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 394.8	$ 170.5	$ 810.4	$ 538.9
Total revenue	394.8	170.5	810.4	538.9
Income (loss) from operations	1.1	(16.1)	(17.5)	(38.6)
Interest expense	(12.8)	(17.9)	(46.6)	(56.2)
Loss on early extinguishment or restructuring of debt	(0.1)	0.0	(12.5)	(9.2)
Loss from equity investees	(2.9)	(1.3)	(4.8)	(4.0)
Other income	0.6	6.9	4.4	73.0
Loss from continuing operations before income taxes	(14.1)	(28.4)	(77.0)	(35.0)
Income tax expense	(0.1)	(1.4)	(3.8)	(3.7)
Loss from continuing operations	(14.2)	(29.8)	(80.8)	(38.7)
Gain (loss) on sale of subsidiary			(159.9)	(39.3)
(Loss) income from discontinued operations (including loss on sale of $200.3 million for the three months ended September 30, 2021 and net loss on sales of $159.9 million and $39.3 million for the nine months ended September 30, 2021 and 2020, respectively)	(200.3)	8.2	(149.9)	(55.4)
Net loss	(214.5)	(21.6)	(230.7)	(94.1)
Net loss attributable to noncontrolling interest and redeemable noncontrolling interest	2.6	4.3	7.9	6.8
Net loss attributable to INNOVATE Corp.	(211.9)	(17.3)	(222.8)	(87.3)
Less: Preferred dividends and deemed dividends from conversions	1.1	0.4	1.7	1.2
Net loss attributable to common stock and participating preferred stockholders	(213.0)	(17.7)	(224.5)	(88.5)
Depreciation and Amortization	8.9	4.5	17.6	13.3
Total depreciation and amortization	12.3	6.8	26.0	20.2
Capital Expenditures	7.0	4.6	15.0	14.6
Discontinued Operations
Revenues from External Customers and Long-Lived Assets [Line Items]
Gain (loss) on sale of subsidiary	(200.3)	0.0		(39.3)
(Loss) income from discontinued operations (including loss on sale of $200.3 million for the three months ended September 30, 2021 and net loss on sales of $159.9 million and $39.3 million for the nine months ended September 30, 2021 and 2020, respectively)	(200.3)	8.2	(149.9)	(55.4)
Infrastructure
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	383.0	160.7	776.3	508.9
Total revenue	383.0	160.8	776.3	509.6
Life Sciences
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	1.6	0.0	2.8	0.0
Spectrum
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	10.2	9.7	31.3	29.3
Operating Segments
Revenues from External Customers and Long-Lived Assets [Line Items]
Depreciation and Amortization	10.8	5.0	21.5	14.9
Infrastructure recognized within cost of revenue	3.4	2.3	8.4	6.9
Operating Segments | Infrastructure
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	383.0	160.8	776.3	509.6
Income (loss) from operations	12.6	6.0	17.0	13.1
Depreciation and Amortization	7.4	2.7	13.1	8.0
Capital Expenditures	6.1	1.4	11.6	4.8
Operating Segments | Life Sciences
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	1.6	0.0	2.8	0.0
Income (loss) from operations	(4.9)	(4.7)	(14.2)	(11.4)
Depreciation and Amortization	0.0	0.0	0.1	0.1
Capital Expenditures	0.0	0.0	0.5	0.1
Operating Segments | Spectrum
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	10.2	9.7	31.3	29.3
Income (loss) from operations	(1.2)	(11.7)	(1.0)	(15.8)
Depreciation and Amortization	1.4	1.7	4.3	5.1
Capital Expenditures	0.9	3.2	2.9	9.6
Operating Segments | Other
Revenues from External Customers and Long-Lived Assets [Line Items]
Income (loss) from operations	(1.0)	(0.4)	(1.6)	(2.1)
Non-operating Corporate
Revenues from External Customers and Long-Lived Assets [Line Items]
Income (loss) from operations	(4.4)	(5.3)	(17.7)	(22.4)
Depreciation and Amortization	0.1	0.1	0.1	0.1
Capital Expenditures	$ 0.0	$ 0.0	$ 0.0	$ 0.1