Financial Instruments and Risk Management - Interest Rate Risk Management Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Jun. 30, 2020	Mar. 31, 2020	Mar. 02, 2020	Dec. 31, 2019
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value of interest rate swaps	$ 785,700,000	$ 146,100,000	$ 785,700,000	$ 146,100,000	$ 743,700,000	$ 728,700,000	$ 512,100,000	$ 213,000,000.0	$ 276,200,000		$ (704,800,000)	[1]
Recognized earnings	2,700,000	2,900,000	7,900,000	3,400,000
Cash flow hedge loss expected to be reclassified within twelve months			10,200,000
Interest Rate Swap
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value of interest rate swaps	(4,800,000)	$ (37,800,000)	(4,800,000)	$ (37,800,000)	$ (7,500,000)		$ (32,800,000)	$ (35,500,000)			$ 0
Interest Rate Swap
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Derivative, notional amount	1,000,000,000		1,000,000,000							$ 1,200,000,000
Interest rate swaps	5,400,000		5,400,000
Interest Rate Swap | Accrued Expenses
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Interest rate swaps	10,200,000		10,200,000
Interest Rate Swap | Other Noncurrent Assets
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Interest rate swaps	5,400,000		5,400,000
Foreign Exchange Contract | Net Investment Hedging | Designated as Hedging Instrument
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Derivative, notional amount	$ 50,000,000		$ 50,000,000

[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).