Segment Information (Details) - USD ($) $ in Millions		1 Months Ended	2 Months Ended	3 Months Ended		7 Months Ended		9 Months Ended
	Aug. 11, 2023	Aug. 11, 2023	Sep. 30, 2023	Jun. 30, 2023	Sep. 30, 2022	Aug. 11, 2023		Sep. 30, 2022
Summary of Segment Information
Total revenue		$ 351.6	$ 591.8		$ 810.4	$ 2,131.9		$ 2,491.9
Operating income (loss) / Segment operating profit		(0.5)	(36.9)		(5.5)	5.5		169.4
Asset Impairment Charges		(0.6)	(1.1)		(4.1)	(3.3)		(64.7)
Restructuring and transformation expenses(4)		(5.3)	(6.2)		(20.7)	(38.9)		(98.9)
Other income (expense)		2,239.7	(77.0)		(51.5)	1,453.9		(142.1)
Income (loss) from continuing operations before taxes			(40.1)			1,448.4		(311.5)
Amortization of acquired intangible assets			0.0			(41.8)		(52.8)
Global Retail [Member]
Summary of Segment Information
Total revenue		97.2	181.1		225.0	610.0		742.4
Global Banking
Summary of Segment Information
Total revenue		253.2	409.0		580.3	1,511.0		1,733.3
Other Segments
Summary of Segment Information
Total revenue		1.2	1.7		5.1	10.9		16.2
Operating Segments [Member]
Summary of Segment Information
Operating income (loss) / Segment operating profit		(44.4)	(90.6)		(114.2)	(297.8)		(299.4)
Operating Segments [Member] | Global Retail [Member]
Summary of Segment Information
Total revenue		97.2	181.1		225.0	610.0		742.4
Operating income (loss) / Segment operating profit		(15.1)	(31.3)		(31.1)	(86.2)		(90.0)
Operating Segments [Member] | Global Banking
Summary of Segment Information
Total revenue		253.2	409.0		580.3	1,511.0		1,733.3
Operating income (loss) / Segment operating profit		(29.3)	(59.3)		(83.1)	(211.6)		(209.4)
Corporate and Reconciling Items [Member]
Summary of Segment Information
Reconciliation Of Operating Profit Loss From Segments To Consolidated, Amount		(43.9)	(53.7)		(108.7)	(303.3)		(468.8)
Segment Reconciling Items [Member]
Summary of Segment Information
Operating income (loss) / Segment operating profit		1.3	1.0		5.0	7.9		16.7
Asset Impairment Charges		0.6	1.1		(4.1)	(3.3)		(64.7)
Restructuring and transformation expenses(4)	$ (5.3)	(4.8)	(5.1)	$ (6.2)	(20.7)	(38.4)		(98.9)
Net non-routine expense(6)		(4.7)	0.2		5.3	(7.4)		(34.3)
Amortization of acquired intangible assets		6.1	0.0		(16.6)	(41.8)		(52.8)
Corporate
Summary of Segment Information
Operating income (loss) / Segment operating profit		$ (26.3)	$ (47.0)		$ (54.2)	$ 159.8	[1]	$ 188.0	[1]

[1] Corporate charges not allocated to segments include headquarter-based costs associated primarily with human resources, finance, IT and legal that are not directly attributable to a particular segment and are separately assessed by the CODM for purposes of making decisions, assessing performance and allocating resources. It also includes the impact of $2.8 of revenue reversed due to a legal settlement penalty during the Successor Period. (2)    Impairment in the 2023 Successor Period primarily relates to German and Indian facilities. Impairment in the 2023 Predecessor Periods primarily relate to leased European facilities closures. Impairment during the nine months ended September 30, 2022 Predecessor Period was primarily comprised of $38.4 related to impairment of capitalized cloud-based North America ERP, and the Company impaired $16.8 of assets connected with the Company's operations in Russia, Ukraine and Belarus as a result of the Russian incursion into Ukraine and the related economic sanctions. (3)    The amortization of purchase accounting intangible assets is not included in the segment results used by the CODM to make decisions, allocate resources or assess performance. (4)    Refer to Note 11 for further information regarding restructurings. Consistent with the historical reportable segment structure, restructuring and transformation costs are not assigned to the segments, and are separately analyzed by the CODM. (5)    Refinancing related costs are fees earned by our advisors that have been accounted for as period expense. (6)    Net non-routine expense consists of items that the Company has determined are non-routine in nature and not allocated to the reportable operating segments as they are not included in the measure used by the CODM to make decisions, allocate resources and assess performance. (7)    Held for sale non-core European retail business represents the revenue and operating profit of a business that had been classified as held for sale in the Predecessor Period and sold during the Successor Period (see Note 15). It was removed in 2022 from the retail segment's information used by the CODM to make decisions, assess performance and allocate resources, and now is individually analyzed. This change and timing thereof aligns with the build-out of a data center that makes the entity capable of operating autonomously and is consistent with material provided in connection with our refinancing effort which are exclusive of this entity. (8)    Excludes $2.8 of revenue reversed due to a legal settlement penalty during the Successor period.