Business Segments - Results of Operations and Average Assets by Segment (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting Information
Total goodwill	$ 4,514	$ 4,261	$ 4,514	$ 4,261	$ 4,258	$ 4,252
Total assets	207,731	201,996	207,731	201,996
Net interest income	1,189	1,170	3,574	3,600
(Benefit from) provision for credit losses	(42)	(15)	(330)	1,110
Net Interest Income After (Benefit from) Provision for Credit Losses	1,231	1,185	3,904	2,490
Noninterest Income
Commercial banking revenue	152	125	465	387
Service charges on deposits	152	144	445	414
Wealth and asset management revenue	147	132	436	387
Card and processing revenue	102	92	298	260
Mortgage banking net revenue	86	76	235	295
Leasing business revenue	78	77	226	207
Other noninterest income	120	26	211	42
Securities (losses) gains, net	(1)	51	12	48
Securities losses, net – non-qualifying hedges on MSRs	0	(1)	(2)	3
Total noninterest income	836	722	2,326	2,043
Noninterest Expense
Compensation and benefits	627	637	1,971	1,911
Technology and communications	98	89	285	272
Net occupancy expense	79	90	235	254
Equipment expense	34	33	102	97
Leasing business expense	33	35	102	103
Marketing expense	29	23	72	74
Card and processing expense	19	29	70	89
Other noninterest expense	253	225	704	682
Total noninterest expense	1,172	1,161	3,541	3,482
Income before income taxes	895	746	2,689	1,051
Applicable income tax expense (benefit)	191	165	582	228
Net Income	704	581	2,107	823
Impairment losses on bank premises	3	11	7	25
Impairment losses of operating lease equipment			25	3
Impairment losses and termination charges	1	1	3	6
Bank premises and equipment held for sale	25		25		35
General Corporate and Other
Segment Reporting Information
Total goodwill	0	0	0	0
Total assets	3,943	13,564	3,943	13,564
Net interest income	344	257	1,080	321
(Benefit from) provision for credit losses	189	(422)	55	64
Net Interest Income After (Benefit from) Provision for Credit Losses	155	679	1,025	257
Noninterest Income
Commercial banking revenue	0	(1)	0	(3)
Service charges on deposits	0	0	0	0
Wealth and asset management revenue	0	0	0	0
Card and processing revenue	2	3	7	10
Mortgage banking net revenue	0	0	0	0
Leasing business revenue	0	0	0	0
Other noninterest income	65	(7)	63	(37)
Securities (losses) gains, net	(3)	51	4	48
Securities losses, net – non-qualifying hedges on MSRs	0	0	0	0
Total noninterest income	64	46	74	18
Noninterest Expense
Compensation and benefits	220	237	712	688
Technology and communications	89	83	260	253
Net occupancy expense	17	33	47	84
Equipment expense	18	17	55	46
Leasing business expense	0	0	0	0
Marketing expense	16	14	41	41
Card and processing expense	(1)	(1)	(3)	(3)
Other noninterest expense	(302)	(324)	(948)	(988)
Total noninterest expense	57	59	164	121
Income before income taxes	162	666	935	154
Applicable income tax expense (benefit)	45	158	243	71
Net Income	117	508	692	83
Impairment losses on bank premises		4	1	14
Bank premises and equipment held for sale	25	45	25	45
Eliminations
Segment Reporting Information
Total goodwill	0	0	0	0
Total assets	0	0	0	0
Net interest income	0	0	0	0
(Benefit from) provision for credit losses	0	0	0	0
Net Interest Income After (Benefit from) Provision for Credit Losses	0	0	0	0
Noninterest Income
Commercial banking revenue	0	0	0	0
Service charges on deposits	0	0	0	0
Wealth and asset management revenue	(46)	(39)	(134)	(114)
Card and processing revenue	0	0	0	0
Mortgage banking net revenue	0	0	0	0
Leasing business revenue	0	0	0	0
Other noninterest income	0	0	0	0
Securities (losses) gains, net	0	0	0	0
Securities losses, net – non-qualifying hedges on MSRs	0	0	0	0
Total noninterest income	(46)	(39)	(134)	(114)
Noninterest Expense
Compensation and benefits	0	0	0	0
Technology and communications	0	0	0	0
Net occupancy expense	0	0	0	0
Equipment expense	0	0	0	0
Leasing business expense	0	0	0	0
Marketing expense	0	0	0	0
Card and processing expense	0	0	0	0
Other noninterest expense	(46)	(39)	(134)	(114)
Total noninterest expense	(46)	(39)	(134)	(114)
Income before income taxes	0	0	0	0
Applicable income tax expense (benefit)	0	0	0	0
Net Income	0	0	0	0
Commercial Banking
Segment Reporting Information
Total goodwill	1,981		1,981		1,980	1,954
Noninterest Expense
Impairment losses of operating lease equipment			25	3
Commercial Banking | Operating Segments
Segment Reporting Information
Total goodwill	1,981	1,961	1,981	1,961
Total assets	70,346	72,025	70,346	72,025
Net interest income	369	432	1,110	1,512
(Benefit from) provision for credit losses	(242)	337	(470)	839
Net Interest Income After (Benefit from) Provision for Credit Losses	611	95	1,580	673
Noninterest Income
Commercial banking revenue	150	125	457	386
Service charges on deposits	91	91	273	253
Wealth and asset management revenue	0	1	2	2
Card and processing revenue	17	13	45	40
Mortgage banking net revenue	0	0	0	0
Leasing business revenue	78	77	226	207
Other noninterest income	24	11	66	9
Securities (losses) gains, net	2	0	8	0
Securities losses, net – non-qualifying hedges on MSRs	0	0	0	0
Total noninterest income	362	318	1,077	897
Noninterest Expense
Compensation and benefits	138	127	431	405
Technology and communications	5	3	12	10
Net occupancy expense	8	8	25	23
Equipment expense	7	6	19	20
Leasing business expense	33	35	102	103
Marketing expense	1	2	4	5
Card and processing expense	2	2	5	6
Other noninterest expense	212	228	627	722
Total noninterest expense	406	411	1,225	1,294
Income before income taxes	567	2	1,432	276
Applicable income tax expense (benefit)	110	(10)	270	27
Net Income	457	12	1,162	249
Branch Banking
Segment Reporting Information
Total goodwill	2,302		2,302		2,047	2,046
Branch Banking | Operating Segments
Segment Reporting Information
Total goodwill	2,302	2,047	2,302	2,047
Total assets	88,732	77,018	88,732	77,018
Net interest income	309	355	905	1,372
(Benefit from) provision for credit losses	13	68	79	182
Net Interest Income After (Benefit from) Provision for Credit Losses	296	287	826	1,190
Noninterest Income
Commercial banking revenue	2	1	7	3
Service charges on deposits	61	53	172	160
Wealth and asset management revenue	53	44	154	128
Card and processing revenue	82	76	244	209
Mortgage banking net revenue	3	2	8	6
Leasing business revenue	0	0	0	0
Other noninterest income	28	16	73	49
Securities (losses) gains, net	0	0	0	0
Securities losses, net – non-qualifying hedges on MSRs	0	0	0	0
Total noninterest income	229	192	658	555
Noninterest Expense
Compensation and benefits	160	162	488	491
Technology and communications	1	1	4	2
Net occupancy expense	48	44	144	131
Equipment expense	9	10	28	31
Leasing business expense	0	0	0	0
Marketing expense	10	6	24	23
Card and processing expense	18	28	68	86
Other noninterest expense	217	209	647	635
Total noninterest expense	463	460	1,403	1,399
Income before income taxes	62	19	81	346
Applicable income tax expense (benefit)	14	4	17	73
Net Income	48	15	64	273
Impairment losses on bank premises	3	7	6	11
Consumer Lending
Segment Reporting Information
Total goodwill	0		0		0	0
Consumer Lending | Operating Segments
Segment Reporting Information
Total goodwill	0	0	0	0
Total assets	33,438	27,869	33,438	27,869
Net interest income	145	98	415	279
(Benefit from) provision for credit losses	(2)	2	7	25
Net Interest Income After (Benefit from) Provision for Credit Losses	147	96	408	254
Noninterest Income
Commercial banking revenue	0	0	0	0
Service charges on deposits	0	0	0	0
Wealth and asset management revenue	0	0	0	0
Card and processing revenue	0	0	0	0
Mortgage banking net revenue	82	72	225	286
Leasing business revenue	0	0	0	0
Other noninterest income	2	2	6	8
Securities (losses) gains, net	0	0	0	0
Securities losses, net – non-qualifying hedges on MSRs	0	(1)	(2)	3
Total noninterest income	84	73	229	297
Noninterest Expense
Compensation and benefits	61	57	189	162
Technology and communications	3	2	8	6
Net occupancy expense	2	2	8	7
Equipment expense	0	0	0	0
Leasing business expense	0	0	0	0
Marketing expense	1	1	2	3
Card and processing expense	0	0	0	0
Other noninterest expense	91	75	276	204
Total noninterest expense	158	137	483	382
Income before income taxes	73	32	154	169
Applicable income tax expense (benefit)	15	7	33	35
Net Income	58	25	121	134
Wealth and Asset Management
Segment Reporting Information
Total goodwill	231		231		$ 231	$ 252
Wealth and Asset Management | Operating Segments
Segment Reporting Information
Total goodwill	231	253	231	253
Total assets	11,272	11,520	11,272	11,520
Net interest income	22	28	64	116
(Benefit from) provision for credit losses	0	0	(1)	0
Net Interest Income After (Benefit from) Provision for Credit Losses	22	28	65	116
Noninterest Income
Commercial banking revenue	0	0	1	1
Service charges on deposits	0	0	0	1
Wealth and asset management revenue	140	126	414	371
Card and processing revenue	1	0	2	1
Mortgage banking net revenue	1	2	2	3
Leasing business revenue	0	0	0	0
Other noninterest income	1	4	3	13
Securities (losses) gains, net	0	0	0	0
Securities losses, net – non-qualifying hedges on MSRs	0	0	0	0
Total noninterest income	143	132	422	390
Noninterest Expense
Compensation and benefits	48	54	151	165
Technology and communications	0	0	1	1
Net occupancy expense	4	3	11	9
Equipment expense	0	0	0	0
Leasing business expense	0	0	0	0
Marketing expense	1	0	1	2
Card and processing expense	0	0	0	0
Other noninterest expense	81	76	236	223
Total noninterest expense	134	133	400	400
Income before income taxes	31	27	87	106
Applicable income tax expense (benefit)	7	6	19	22
Net Income	$ 24	$ 21	$ 68	$ 84