Goodwill and Intangible Assets - Changes in Carrying Amounts of Goodwill by Reportable Segment (Details) - USD ($) $ in Millions					3 Months Ended				12 Months Ended
	Feb. 29, 2024	Oct. 01, 2023	Mar. 31, 2023	Jan. 01, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Goodwill [Line Items]
Goodwill, Gross							$ 3,037.0		$ 2,159.4	$ 2,161.2	$ 3,037.0
Less: Accumulated impairment charges							(881.9)		(1,423.7)	(708.8)	(881.9)
Goodwill [Roll Forward]
Goodwill, beginning balance				$ 2,155.1					1,452.4	2,155.1
Reallocation adjustment										0.0
Impairment of goodwill		$ 0.0							(714.9)	(708.8)	(534.5)
Foreign currency translation									(1.8)	6.1
Goodwill, ending balance							2,155.1		735.7	1,452.4	2,155.1
Previously Reported
Goodwill [Line Items]
Goodwill, Gross									3,041.3
Less: Accumulated impairment charges									(2,305.6)
Public Cloud
Goodwill [Line Items]
Goodwill, Gross							0.0		596.2	597.7	0.0
Less: Accumulated impairment charges							0.0		(454.6)	0.0	0.0
Goodwill [Roll Forward]
Goodwill, beginning balance				0.0					597.7	0.0
Reallocation adjustment										594.7
Impairment of goodwill	$ (385.4)				$ (69.2)				(454.6)	0.0
Foreign currency translation									(1.5)	3.0
Goodwill, ending balance							0.0		141.6	597.7	0.0
Private Cloud
Goodwill [Line Items]
Goodwill, Gross							0.0		1,563.2	1,563.5	0.0
Less: Accumulated impairment charges							0.0		(969.1)	(708.8)	0.0
Goodwill [Roll Forward]
Goodwill, beginning balance				0.0					854.7	0.0
Reallocation adjustment										1,560.4
Impairment of goodwill	$ (187.8)		$ (272.3)	(270.8)	$ (72.5)	$ (165.7)			(260.3)	(708.8)
Foreign currency translation									(0.3)	3.1
Goodwill, ending balance							0.0		594.1	854.7	0.0
Multicloud Services
Goodwill [Line Items]
Goodwill, Gross							2,656.6		0.0	0.0	2,656.6
Less: Accumulated impairment charges							(700.2)		0.0	0.0	(700.2)
Goodwill [Roll Forward]
Goodwill, beginning balance				1,956.4					0.0	1,956.4
Reallocation adjustment										(1,956.4)
Impairment of goodwill								$ (405.2)	0.0	0.0
Foreign currency translation									0.0	0.0
Goodwill, ending balance							1,956.4		0.0	0.0	1,956.4
Apps & Cross Platform
Goodwill [Line Items]
Goodwill, Gross							328.0		0.0	0.0	328.0
Less: Accumulated impairment charges							(129.3)		0.0	0.0	(129.3)
Goodwill [Roll Forward]
Goodwill, beginning balance				198.7					0.0	198.7
Reallocation adjustment										(198.7)
Impairment of goodwill							(129.3)		0.0	0.0
Foreign currency translation									0.0	0.0
Goodwill, ending balance							198.7		0.0	0.0	198.7
OpenStack Public Cloud
Goodwill [Line Items]
Goodwill, Gross							52.4		0.0	0.0	52.4
Less: Accumulated impairment charges							(52.4)		0.0	0.0	(52.4)
Goodwill [Roll Forward]
Goodwill, beginning balance				$ 0.0					0.0	0.0
Reallocation adjustment										0.0
Impairment of goodwill									0.0	0.0
Foreign currency translation									0.0	0.0
Goodwill, ending balance							$ 0.0		$ 0.0	$ 0.0	$ 0.0