Goodwill and Other Assets (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2023	Dec. 31, 2022
Goodwill [Line Items]
Goodwill	$ 1,184.3	$ 1,184.3	$ 1,173.2
Accumulated impairment losses	(470.9)	(470.9)	(470.9)
Beginning balance		702.3
Goodwill, Foreign Currency Translation Gain (Loss)		11.1
Ending balance	713.4	713.4
Global Retail [Member]
Goodwill [Line Items]
Goodwill	273.0	273.0	269.6
Accumulated impairment losses	(57.2)	(57.2)	(57.2)
Beginning balance		212.4
Goodwill, Foreign Currency Translation Gain (Loss)		3.4
Ending balance	$ 215.8	215.8
Segment Reporting, Additional Information about Entity's Reportable Segments	34 percent
Global Banking
Goodwill [Line Items]
Goodwill	$ 911.3	911.3	903.6
Accumulated impairment losses	(413.7)	(413.7)	$ (413.7)
Beginning balance		489.9
Goodwill, Foreign Currency Translation Gain (Loss)		7.7
Ending balance	$ 497.6	$ 497.6
Segment Reporting, Additional Information about Entity's Reportable Segments	43 percent