Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019		Dec. 31, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	[1]	$ (704.8)	$ (540.3)		$ (129.6)
Ending balance		668.3	(704.8)	[1]	(540.3)	[1]
Foreign Currency Translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		32.9	43.2		133.8
Other comprehensive income (loss)		72.0	(10.3)		(90.6)
Ending balance		104.9	32.9		43.2
Interest Rate Swap
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		0.0	0.0		0.0
Other comprehensive income (loss)		(32.8)	0.0		0.0
Ending balance		(32.8)	0.0		0.0
Pension
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		(14.8)	(1.4)		(0.3)
Other comprehensive income (loss)		(4.9)	(13.4)		(1.1)
Ending balance		(19.7)	(14.8)		(1.4)
Tax Receivable Agreement
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		0.0	0.0		0.0
Other comprehensive income (loss)		(0.9)	0.0		0.0
Ending balance		(0.9)	0.0		0.0
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	[1]	18.1	41.8		133.5
Ending balance		$ 51.5	$ 18.1	[1]	$ 41.8	[1]

[1] The shares and earnings per share available to holders of the Company’s common shares, 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).