Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Statement of Comprehensive Income [Abstract]
Net (loss) income	$ (25.2)	$ 28.5	$ (16.2)	$ (72.5)
Other comprehensive income (loss)
Foreign currency translation adjustment	(0.4)	3.8	(1.2)	4.0
Unrealized income (loss) on available-for-sale securities	123.5	283.8	(57.7)	7.8
Dispositions	0.0	(0.7)	0.0	22.1
Other comprehensive income (loss)	123.1	286.9	(58.9)	33.9
Comprehensive income (loss)	97.9	315.4	(75.1)	(38.6)
Comprehensive (loss) income attributable to noncontrolling interests and redeemable noncontrolling interests	(1.7)	16.2	(5.4)	7.3
Comprehensive income (loss) attributable to HC2 Holdings, Inc.	$ 96.2	$ 331.6	$ (80.5)	$ (31.3)