Accumulated Other Comprehensive Income (Loss) - Schedule of Activity in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 743.7	$ 213.0	$ 512.1	$ (704.8)	[1]
Other comprehensive income (loss), net of tax	(23.0)	32.7	(19.5)	(29.2)
Ending balance	785.7	146.1	785.7	146.1
Recognized earnings	2.7	2.9	7.9	3.4
Foreign Currency Translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	89.0	(9.5)	104.9	32.9
Other comprehensive income (loss), net of tax	(28.0)	46.1	(43.9)	3.7
Ending balance	61.0	36.6	61.0	36.6
Interest Rate Swap
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(7.5)	(35.5)	(32.8)	0.0
Other comprehensive income (loss), net of tax	2.7	(2.3)	28.0	(37.8)
Ending balance	(4.8)	(37.8)	(4.8)	(37.8)
Pension
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(20.3)	(15.0)	(19.7)	(14.8)
Other comprehensive income (loss), net of tax	0.1	0.0	(0.5)	(0.2)
Ending balance	(20.2)	(15.0)	(20.2)	(15.0)
Tax Receivable Agreement
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(6.2)	16.2	(0.9)	0.0
Other comprehensive income (loss), net of tax	2.2	(11.1)	(3.1)	5.1
Ending balance	(4.0)	5.1	(4.0)	5.1
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	55.0	(43.8)	51.5	18.1	[1]
Ending balance	$ 32.0	$ (11.1)	$ 32.0	$ (11.1)

[1] The shares and earnings per share available to holders of the Company’s capital stock, prior to the business combination, have been recasted as shares reflecting the exchange ratio established in the business combination (1.0 Vertiv Holdings share to 118.261955 Vertiv Holdings Co shares).