Unaudited Condensed Consolidated Statements of Shareholders' Equity (Deficit) - USD ($) $ in Millions		Total	Share Capital		Share Capital Previously Reported	Share Capital Restatement Adjustment	Additional Paid in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)
Beginning balance (in shares) at Dec. 31, 2019			118,261,955	[1]	1,000,000.0	117,261,955
Beginning balance at Dec. 31, 2019	[1]	$ (704.8)	$ 0.0				$ 277.7	$ (1,000.6)	$ 18.1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Tax Receivable Agreement		(133.4)					(133.4)
Net income (loss)		(208.3)						(208.3)
Stock issuance (in shares)			123,900,000
Stock issuance		1,195.1					1,195.1
Merger recapitalization (in shares)	[2]		86,249,750
Merger recapitalization	[2]	179.5					179.5
Stock-based compensation		0.7					0.7
Other comprehensive income (loss), net of tax		(52.6)							(52.6)
Ending balance (in shares) at Mar. 31, 2020			328,411,705
Ending balance at Mar. 31, 2020		276.2	$ 0.0				1,519.6	(1,208.9)	(34.5)
Beginning balance (in shares) at Dec. 31, 2019			118,261,955	[1]	1,000,000.0	117,261,955
Beginning balance at Dec. 31, 2019	[1]	(704.8)	$ 0.0				277.7	(1,000.6)	18.1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)		(367.8)
Ending balance (in shares) at Sep. 30, 2020			328,411,705
Ending balance at Sep. 30, 2020		146.1	$ 0.0				1,525.6	(1,368.4)	(11.1)
Beginning balance (in shares) at Dec. 31, 2019			118,261,955	[1]	1,000,000.0	117,261,955
Beginning balance at Dec. 31, 2019	[1]	$ (704.8)	$ 0.0				277.7	(1,000.6)	18.1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Tax Receivable Agreement							(133.4)
Ending balance (in shares) at Dec. 31, 2020		342,024,612	342,024,612
Ending balance at Dec. 31, 2020		$ 512.1	$ 0.0				1,791.8	(1,331.2)	51.5
Beginning balance (in shares) at Mar. 31, 2020			328,411,705
Beginning balance at Mar. 31, 2020		276.2	$ 0.0				1,519.6	(1,208.9)	(34.5)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)		(56.0)						(56.0)
Stock-based compensation		2.5					2.5
Other merger adjustment		(0.4)					(0.4)
Other comprehensive income (loss), net of tax		(9.3)							(9.3)
Ending balance (in shares) at Jun. 30, 2020			328,411,705
Ending balance at Jun. 30, 2020		213.0	$ 0.0				1,521.7	(1,264.9)	(43.8)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)		(103.5)						(103.5)
Stock-based compensation		3.9					3.9
Other merger adjustment		0.0
Other comprehensive income (loss), net of tax		32.7							32.7
Ending balance (in shares) at Sep. 30, 2020			328,411,705
Ending balance at Sep. 30, 2020		$ 146.1	$ 0.0				1,525.6	(1,368.4)	(11.1)
Beginning balance (in shares) at Dec. 31, 2020		342,024,612	342,024,612
Beginning balance at Dec. 31, 2020		$ 512.1	$ 0.0				1,791.8	(1,331.2)	51.5
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)		31.7						31.7
Exercise of employee stock options (in shares)			76,047
Exercise of employee stock options		0.9					0.9
Employee 401K match with Vertiv stock (in shares)			69,309
Employee 401K match with Vertiv stock		1.3					1.3
Exercise of warrants (in shares)	[3]		9,346,822
Exercise of warrants	[3]	176.0					176.0
Stock-based compensation		5.6					5.6
Other comprehensive income (loss), net of tax		1.1							1.1
Ending balance (in shares) at Mar. 31, 2021			351,516,790
Ending balance at Mar. 31, 2021		$ 728.7	$ 0.0				1,975.6	(1,299.5)	52.6
Beginning balance (in shares) at Dec. 31, 2020		342,024,612	342,024,612
Beginning balance at Dec. 31, 2020		$ 512.1	$ 0.0				1,791.8	(1,331.2)	51.5
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)		$ 97.6
Ending balance (in shares) at Sep. 30, 2021		352,499,706	352,499,706
Ending balance at Sep. 30, 2021		$ 785.7	$ 0.0				1,987.3	(1,233.6)	32.0
Beginning balance (in shares) at Mar. 31, 2021			351,516,790
Beginning balance at Mar. 31, 2021		728.7	$ 0.0				1,975.6	(1,299.5)	52.6
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)		9.7						9.7
Exercise of employee stock options (in shares)			120,721
Exercise of employee stock options		1.4					1.4
Stock comp activity, net of withholdings for tax (in shares)	[4]		586,139
Stock comp activity, net of withholdings for tax	[4]	(0.8)					(0.8)
Employee 401K match with Vertiv stock (in shares)			107,890
Employee 401K match with Vertiv stock		2.3					2.3
Other comprehensive income (loss), net of tax		2.4							2.4
Ending balance (in shares) at Jun. 30, 2021			352,331,540
Ending balance at Jun. 30, 2021		743.7	$ 0.0				1,978.5	(1,289.8)	55.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)		56.2						56.2
Exercise of employee stock options (in shares)			51,122
Exercise of employee stock options		0.8					0.8
Stock comp activity, net of withholdings for tax (in shares)	[5]		27,069
Stock comp activity, net of withholdings for tax	[5]	5.5					5.5
Employee 401K match with Vertiv stock (in shares)			89,975
Employee 401K match with Vertiv stock		2.5					2.5
Other comprehensive income (loss), net of tax		$ (23.0)							(23.0)
Ending balance (in shares) at Sep. 30, 2021		352,499,706	352,499,706
Ending balance at Sep. 30, 2021		$ 785.7	$ 0.0				$ 1,987.3	$ (1,233.6)	$ 32.0

[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).

[2] The merger recapitalization includes the fair value of $116.3 of Public Warrants and Private Placement Warrants as of February 7, 2020.

[3] The exercise of warrants includes $107.5 of cash received during the three months ended March 31, 2021 for the exercise of Public Warrants.

[4] Net stock compensation activity includes 906,197 vested shares offset by 320,058 shares withheld for taxes valued at $7.0 and stock-based compensation of $6.2.

[5] Net stock compensation activity includes 29,605 vested shares offset by 2,536 shares withheld for taxes valued at $0.2 and stock-based compensation of $5.7.