Loans and Allowance for Credit Losses - Activity in Allowance for Credit Losses (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 7,904	$ 7,523	$ 7,839	$ 7,404
Add
Allowance for acquired credit losses				127
Provision for credit losses	568	821	1,121	1,248
Deduct
Loans charged-off	652	755	1,247	1,224
Less recoveries of loans charged-off	(114)	(106)	(221)	(202)
Net loan charge-offs (recoveries)	538	649	1,026	1,022
Balance at end of period	7,934	7,695	7,934	7,695
Change in accounting principle
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period				(62)
Commercial | Commercial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	2,159	2,180	2,119	2,163
Add
Allowance for acquired credit losses				0
Provision for credit losses	164	119	320	183
Deduct
Loans charged-off	180	110	319	173
Less recoveries of loans charged-off	(37)	(20)	(60)	(36)
Net loan charge-offs (recoveries)	143	90	259	137
Balance at end of period	2,180	2,209	2,180	2,209
Commercial | Commercial | Change in accounting principle
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period				0
Commercial | Commercial real estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	1,629	1,359	1,620	1,325
Add
Allowance for acquired credit losses				127
Provision for credit losses	3	140	33	164
Deduct
Loans charged-off	38	31	72	154
Less recoveries of loans charged-off	(2)	(5)	(15)	(11)
Net loan charge-offs (recoveries)	36	26	57	143
Balance at end of period	1,596	1,473	1,596	1,473
Commercial | Commercial real estate | Change in accounting principle
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period				0
Consumer | Residential mortgages
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	843	947	827	926
Add
Allowance for acquired credit losses				0
Provision for credit losses	(11)	66	5	117
Deduct
Loans charged-off	3	121	7	125
Less recoveries of loans charged-off	(7)	(7)	(11)	(12)
Net loan charge-offs (recoveries)	(4)	114	(4)	113
Balance at end of period	836	899	836	899
Consumer | Residential mortgages | Change in accounting principle
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period				(31)
Consumer | Credit card
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	2,425	2,112	2,403	2,020
Add
Allowance for acquired credit losses				0
Provision for credit losses	388	272	706	566
Deduct
Loans charged-off	358	242	695	457
Less recoveries of loans charged-off	(43)	(43)	(84)	(83)
Net loan charge-offs (recoveries)	315	199	611	374
Balance at end of period	2,498	2,185	2,498	2,185
Consumer | Credit card | Change in accounting principle
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period				(27)
Consumer | Other retail
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	848	925	870	970
Add
Allowance for acquired credit losses				0
Provision for credit losses	24	224	57	218
Deduct
Loans charged-off	73	251	154	315
Less recoveries of loans charged-off	(25)	(31)	(51)	(60)
Net loan charge-offs (recoveries)	48	220	103	255
Balance at end of period	$ 824	$ 929	$ 824	929
Consumer | Other retail | Change in accounting principle
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period				$ (4)