Condensed Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Statement [Abstract]
Revenue	$ 243.8	$ 181.8	$ 415.6	$ 368.4
Cost of revenue	207.4	152.1	348.7	308.9
Gross profit	36.4	29.7	66.9	59.5
Operating expenses:
Selling, general and administrative	39.5	36.4	76.6	75.3
Depreciation and amortization	4.8	4.5	8.7	8.8
Other operating (income) loss	(0.2)	(2.3)	0.2	(2.1)
Loss from operations	(7.7)	(8.9)	(18.6)	(22.5)
Other (expense) income:
Interest expense	(12.4)	(19.1)	(33.8)	(38.3)
Loss on early extinguishment or restructuring of debt	(1.6)	(3.4)	(12.4)	(9.2)
Income (loss) from equity investees	0.2	(0.2)	(1.9)	(2.7)
Other income	0.4	64.6	3.8	66.1
(Loss) income from continuing operations before income taxes	(21.1)	33.0	(62.9)	(6.6)
Income tax expense	(2.6)	(12.0)	(3.7)	(2.3)
(Loss) income from continuing operations	(23.7)	21.0	(66.6)	(8.9)
(Loss) income from discontinued operations (including gain on disposal of $40.4 million and loss on disposal of $39.3 million for the six months ended June 30, 2021 and 2020, respectively)	(1.5)	7.5	50.4	(63.6)
Net (loss) income	(25.2)	28.5	(16.2)	(72.5)
Net income (loss) attributable to noncontrolling interest and redeemable noncontrolling interest	1.7	(15.4)	5.3	2.5
Net (loss) income attributable to HC2 Holdings, Inc.	(23.5)	13.1	(10.9)	(70.0)
Less: Preferred dividends and deemed dividends from conversions	0.2	0.4	0.6	0.8
Net (loss) income attributable to common stock and participating preferred stockholders	$ (23.7)	$ 12.7	$ (11.5)	$ (70.8)
(Loss) income per common share - continuing operations
Basic (in usd per share)	$ (0.29)	$ 0.11	$ (0.82)	$ (0.48)
Diluted (in usd per share)	(0.29)	0.11	(0.82)	(0.48)
(Loss) income per common share - discontinued operations
Basic (in usd per share)	(0.02)	0.15	0.67	(1.06)
Diluted (in usd per share)	(0.02)	0.14	0.67	(1.06)
(Loss) income per share - Net (loss) income attributable to common stock and participating preferred stockholders
Basic (in usd per share)	(0.31)	0.26	(0.15)	(1.54)
Diluted (in usd per share)	$ (0.31)	$ 0.25	$ (0.15)	$ (1.54)
Weighted average common shares outstanding:
Basic (in shares)	77.0	46.8	77.1	45.9
Diluted (in shares)	77.0	48.8	77.1	45.9