Segment Information - Information about Company's Segments (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Segment Reporting Information [Line Items]
Net Income (Loss)	$ 655	$ 867	$ 1,186	$ 1,569
Total Average Assets	211,981	204,376	211,729	203,492
Operating Segments
Segment Reporting Information [Line Items]
Total Revenues	2,302	2,602	4,562	5,007
Inter- segment Revenues
Segment Reporting Information [Line Items]
Total Revenues	0	0	0	0
Commercial Bank
Segment Reporting Information [Line Items]
Net Income (Loss)	205	235	406	568
Total Average Assets	81,198	80,985	81,140	80,014
Commercial Bank | Operating Segments
Segment Reporting Information [Line Items]
Total Revenues	717	759	1,416	1,570
Commercial Bank | Inter- segment Revenues
Segment Reporting Information [Line Items]
Total Revenues	2	1	4	3
Retail Bank
Segment Reporting Information [Line Items]
Net Income (Loss)	472	475	918	927
Total Average Assets	52,950	51,058	52,591	51,175
Retail Bank | Operating Segments
Segment Reporting Information [Line Items]
Total Revenues	1,294	1,296	2,562	2,530
Retail Bank | Inter- segment Revenues
Segment Reporting Information [Line Items]
Total Revenues	0	0	0	0
Institutional Services and Wealth Management
Segment Reporting Information [Line Items]
Net Income (Loss)	144	285	272	395
Total Average Assets	3,668	3,720	3,652	3,688
Institutional Services and Wealth Management | Operating Segments
Segment Reporting Information [Line Items]
Total Revenues	401	591	778	981
Institutional Services and Wealth Management | Inter- segment Revenues
Segment Reporting Information [Line Items]
Total Revenues	3	3	6	6
All Other
Segment Reporting Information [Line Items]
Net Income (Loss)	(166)	(128)	(410)	(321)
Total Average Assets	74,165	68,613	74,346	68,615
All Other | Operating Segments
Segment Reporting Information [Line Items]
Total Revenues	(110)	(44)	(194)	(74)
All Other | Inter- segment Revenues
Segment Reporting Information [Line Items]
Total Revenues	$ (5)	$ (4)	$ (10)	$ (9)