Goodwill and Other Assets (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Dec. 31, 2022
Goodwill [Line Items]
Goodwill	$ 1,173.1	$ 1,173.2
Accumulated impairment losses	(470.9)	(470.9)
Beginning balance	702.3
Goodwill, Foreign Currency Translation Gain (Loss)	(0.1)
Ending balance	702.2
Global Retail [Member]
Goodwill [Line Items]
Goodwill	269.6	269.6
Accumulated impairment losses	(57.2)	(57.2)
Beginning balance	212.4
Goodwill, Foreign Currency Translation Gain (Loss)	0.0
Ending balance	$ 212.4
Segment Reporting, Additional Information about Entity's Reportable Segments	34 percent
Global Banking
Goodwill [Line Items]
Goodwill	$ 903.5	903.6
Accumulated impairment losses	(413.7)	$ (413.7)
Beginning balance	489.9
Goodwill, Foreign Currency Translation Gain (Loss)	(0.1)
Ending balance	$ 489.8
Segment Reporting, Additional Information about Entity's Reportable Segments	43 percent