Basic and Diluted Income (Loss) Per Common Share - Basic Income (Loss) Per Common Share to Diluted Income (Loss) Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands, shares in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Earnings Per Share [Abstract]
(Loss) income from continuing operations	$ (23,700)	$ 21,000	$ (66,600)	$ (8,900)
Income (loss) attributable to noncontrolling interest and redeemable noncontrolling interest	1,600	(15,300)	4,400	(12,500)
(Loss) income from continuing operations attributable to the Company	(22,100)	5,700	(62,200)	(21,400)
Less: Preferred dividends, deemed dividends and repurchase gains	200	400	600	800
(Loss) income from continuing operations attributable to HC2 common stockholders	(22,300)	5,300	(62,800)	(22,200)
(Loss) income from discontinued operations	(1,500)	7,500	50,400	(63,600)
(Loss) income attributable to noncontrolling interest and redeemable noncontrolling interest	100	(100)	900	15,000
(Loss) income from discontinued operations, net of tax and noncontrolling interest	(1,400)	7,400	51,300	(48,600)
Net (loss) income attributable to common stock and participating preferred stockholders	$ (23,700)	$ 12,700	$ (11,500)	$ (70,800)
Participating shares at end of period:
Weighted-average common stock outstanding (in shares)	77.0	46.8	77.1	45.9
Unvested restricted stock (in shares)		0.3
Preferred stock (as-converted basis) (in shares)		2.1
Total (in shares)	77.0	49.2	77.1	45.9
Percentage of loss allocated to:
Common stock	100.00%	95.10%	100.00%	100.00%
Unvested restricted stock	0.00%	0.60%	0.00%	0.00%
Preferred stock	0.00%	4.30%	0.00%	0.00%
Net (loss) income from continuing operations attributable to common stock, basic	$ (22,300)	$ 5,000	$ (62,800)	$ (22,200)
Net (loss) income from discontinued operations attributable to common stock, basic	(1,400)	7,100	51,300	(48,600)
Net (loss) income attributable to common stock, basic	(23,700)	12,100	(11,500)	(70,800)
Earnings allocable to common shares, diluted:
Effect of assumed shares under the if-converted method for convertible instruments	0	0	0	0
Net (loss) income from continuing operations attributable to common stock, basic	(22,300)	5,000	(62,800)	(22,200)
Net (loss) income from discontinued operations attributable to common stock, basic	(1,400)	7,100	51,300	(48,600)
Net (loss) income attributable to common stock, basic	$ (23,700)	$ 12,100	$ (11,500)	$ (70,800)
Denominator for basic and dilutive earnings per share
Weighted average common shares outstanding - basic (in shares)	77.0	46.8	77.1	45.9
Effect of assumed shares under treasury stock method for stock options and restricted shares and if-converted method for convertible instruments (in shares)	0.0	2.0	0.0	0.0
Weighted average common shares outstanding - diluted (in shares)	77.0	48.8	77.1	45.9
(Loss) income per 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)