Segment Information - (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023		Jun. 30, 2022
Summary of Segment Information
Total revenue	$ 922.2	$ 851.7	$ 1,780.3		$ 1,681.5
Operating income (loss) / Segment operating profit	3.9	91.5	6.0		174.9
Asset Impairment Charges	(1.8)	(5.4)	(2.7)		(60.6)
Restructuring and transformation expenses(4)	(18.6)	(78.3)	(33.6)		(78.3)
Other income (expense)	(697.6)	(41.7)	(785.8)		(90.6)
Income (loss) from continuing operations before taxes	(701.5)	(133.2)	(791.8)		(265.5)
Amortization of acquired intangible assets			(35.7)		(36.1)
Global Retail [Member]
Summary of Segment Information
Total revenue	252.4	255.8	512.8		517.5
Global Banking
Summary of Segment Information
Total revenue	664.9	590.2	1,257.8		1,152.9
Other Segments
Summary of Segment Information
Total revenue	4.9	5.7	9.7		11.1
Operating Segments [Member]
Summary of Segment Information
Operating income (loss) / Segment operating profit	(134.5)	(115.1)	(253.4)		(185.0)
Operating Segments [Member] | Global Retail [Member]
Summary of Segment Information
Total revenue	252.4	255.8	512.8		517.5
Operating income (loss) / Segment operating profit	(32.1)	(34.6)	(71.1)		(58.8)
Operating Segments [Member] | Global Banking
Summary of Segment Information
Total revenue	664.9	590.2	1,257.8		1,152.9
Operating income (loss) / Segment operating profit	(102.4)	(80.5)	(182.3)		(126.2)
Corporate and Reconciling Items [Member]
Summary of Segment Information
Reconciliation Of Operating Profit Loss From Segments To Consolidated, Amount	(138.4)	(206.6)	(259.4)		(359.9)
Segment Reconciling Items [Member]
Summary of Segment Information
Operating income (loss) / Segment operating profit	2.9	5.3	6.6		11.7
Asset Impairment Charges	1.8	(5.4)	(2.7)		(60.6)
Restructuring and transformation expenses(4)	(18.6)	(78.3)	(33.6)		(78.3)
Net non-routine expense(6)	(2.0)	(37.2)	(2.7)		(39.6)
Amortization of acquired intangible assets	18.0	(17.6)	(35.7)		(36.1)
Corporate
Summary of Segment Information
Operating income (loss) / Segment operating profit	$ (64.6)	$ (62.8)	$ 133.5	[1]	$ 133.6	[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. (2)    Impairment in the six months ended June 30, 2023 relates primarily to leased European facilities closures. Impairment during the six months ended June 30, 2022 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 9 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 has been classified as held for sale for all of the periods presented, but which 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.