Segment Information - (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Summary of Segment Information
Total revenue	$ 858.1	$ 829.8
Operating income (loss) / Segment operating profit	2.1	83.4
Asset Impairment Charges	(0.9)	(55.2)
Restructuring and transformation expenses(4)	(15.0)	0.0
Other income (expense)	(88.2)	(48.9)
Income (loss) from continuing operations before taxes	(90.3)	(132.3)
Amortization of acquired intangible assets	(17.7)	(18.5)
Global Retail [Member]
Summary of Segment Information
Total revenue	260.4	261.7
Global Banking
Summary of Segment Information
Total revenue	592.9	562.7
Other Segments
Summary of Segment Information
Total revenue	4.8	5.4
Operating Segments [Member]
Summary of Segment Information
Operating income (loss) / Segment operating profit	(119.0)	(70.3)
Operating Segments [Member] | Global Retail [Member]
Summary of Segment Information
Total revenue	260.4	261.7
Operating income (loss) / Segment operating profit	(39.1)	(24.2)
Operating Segments [Member] | Global Banking
Summary of Segment Information
Total revenue	592.9	562.7
Operating income (loss) / Segment operating profit	(79.9)	(46.1)
Corporate and Reconciling Items [Member]
Summary of Segment Information
Reconciliation Of Operating Profit Loss From Segments To Consolidated, Amount	(121.1)	(153.7)
Segment Reconciling Items [Member]
Summary of Segment Information
Operating income (loss) / Segment operating profit	3.7	6.4
Asset Impairment Charges	0.9	(55.2)
Restructuring and transformation expenses(4)	(15.0)	0.0
Net non-routine expense(6)	(0.7)	(2.4)
Amortization of acquired intangible assets	17.7	(18.5)
Corporate
Summary of Segment Information
Operating income (loss) / Segment operating profit	$ (69.0)	$ (71.2)