Business Segments - Results of Operations and Average Assets by Segment (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information
Total goodwill		$ 4,258	$ 4,252	$ 2,478
Total assets		204,680	169,369	146,069
Net interest income		4,782	4,797	4,140
Provision for credit losses		1,097	471	207
Net Interest Income After Provision for Credit Losses		3,685	4,326	3,933
Noninterest income:
Service charges on deposits	[1]	559	565	549
Commercial banking revenue	[1]	528	460	408
Wealth and asset management revenue	[1]	520	487	444
Card and processing revenue	[1]	352	360	329
Mortgage banking net revenue	[1]	320	287	212
Leasing business revenue	[1]	276	270	114
Other noninterest income	[1]	211	1,064	803
Securities gains, net	[1]	62	40	(54)
Securities gains, net -non-qualifying hedges on MSRs	[1]	2	3	(15)
Total noninterest income	[1]	2,830	3,536	2,790
Noninterest expense:
Compensation and benefits	[1]	2,590	2,418	2,115
Technology and communications	[1]	362	422	285
Net occupancy expense	[1]	350	332	292
Leasing business expense	[1]	140	133	76
Equipment expense	[1]	130	129	123
Card and processing expense	[1]	121	130	123
Marketing expense	[1]	104	162	147
Other noninterest expense		921	934	797
Total noninterest expense	[1]	4,718	4,660	3,958
Income before income taxes		1,797	3,202	2,765
Applicable income tax expense		370	690	572
Net Income		1,427	2,512	2,193
Impairment losses on bank premises		30	28	45
Bank premises and equipment held for sale		35	27
Impairment losses and termination charges		8	15
Commercial Banking
Segment Reporting Information
Total goodwill		1,980	1,954	630
Noninterest expense:
Impairment charges of operating lease equipment		7	3	4
Branch Banking
Segment Reporting Information
Total goodwill		2,047	2,046	1,655
Consumer Lending
Segment Reporting Information
Total goodwill		0	0	0
Wealth and Asset Management
Segment Reporting Information
Total goodwill		231	252	193
Operating Segments | Commercial Banking
Segment Reporting Information
Total goodwill		1,980	1,954	630
Total assets		70,241	74,570	61,630
Net interest income		1,903	2,360	1,713
Provision for credit losses		1,050	183	(26)
Net Interest Income After Provision for Credit Losses		853	2,177	1,739
Noninterest income:
Service charges on deposits		343	308	273
Commercial banking revenue		524	455	402
Wealth and asset management revenue		3	3	3
Card and processing revenue		54	66	58
Mortgage banking net revenue		0	0	0
Leasing business revenue		276	270	114
Other noninterest income		101	85	67
Securities gains, net		0	0	0
Securities gains, net -non-qualifying hedges on MSRs		0	0	0
Total noninterest income		1,301	1,187	917
Noninterest expense:
Compensation and benefits		557	466	344
Technology and communications		13	11	7
Net occupancy expense		31	28	26
Leasing business expense		140	133	76
Equipment expense		27	25	23
Card and processing expense		7	8	4
Marketing expense		8	12	6
Other noninterest expense		938	938	777
Total noninterest expense		1,721	1,621	1,263
Income before income taxes		433	1,743	1,393
Applicable income tax expense		46	319	254
Net Income		387	1,424	1,139
Operating Segments | Branch Banking
Segment Reporting Information
Total goodwill		2,047	2,046	1,655
Total assets		79,982	69,413	61,040
Net interest income		1,667	2,371	2,034
Provision for credit losses		231	224	171
Net Interest Income After Provision for Credit Losses		1,436	2,147	1,863
Noninterest income:
Service charges on deposits		215	260	275
Commercial banking revenue		5	4	5
Wealth and asset management revenue		172	158	150
Card and processing revenue		283	285	266
Mortgage banking net revenue		8	6	5
Leasing business revenue		0	0	0
Other noninterest income		68	89	53
Securities gains, net		0	0	0
Securities gains, net -non-qualifying hedges on MSRs		0	0	0
Total noninterest income		751	802	754
Noninterest expense:
Compensation and benefits		649	601	536
Technology and communications		4	4	5
Net occupancy expense		176	173	175
Leasing business expense		0	0	0
Equipment expense		41	48	50
Card and processing expense		116	123	121
Marketing expense		32	72	67
Other noninterest expense		851	839	774
Total noninterest expense		1,869	1,860	1,728
Income before income taxes		318	1,089	889
Applicable income tax expense		67	229	187
Net Income		251	860	702
Operating Segments | Consumer Lending
Segment Reporting Information
Total goodwill		0	0	0
Total assets		30,480	26,555	22,044
Net interest income		381	325	237
Provision for credit losses		34	49	42
Net Interest Income After Provision for Credit Losses		347	276	195
Noninterest income:
Service charges on deposits		0	0	0
Commercial banking revenue		0	0	0
Wealth and asset management revenue		0	0	0
Card and processing revenue		0	0	0
Mortgage banking net revenue		307	279	206
Leasing business revenue		0	0	0
Other noninterest income		10	14	14
Securities gains, net		0	0	0
Securities gains, net -non-qualifying hedges on MSRs		2	3	(15)
Total noninterest income		319	296	205
Noninterest expense:
Compensation and benefits		221	196	192
Technology and communications		8	8	5
Net occupancy expense		10	10	10
Leasing business expense		0	0	0
Equipment expense		0	0	0
Card and processing expense		0	0	0
Marketing expense		3	4	4
Other noninterest expense		276	237	191
Total noninterest expense		518	455	402
Income before income taxes		148	117	(2)
Applicable income tax expense		31	25	(1)
Net Income		117	92	(1)
Operating Segments | Wealth and Asset Management
Segment Reporting Information
Total goodwill		231	252	193
Total assets		12,466	10,500	10,337
Net interest income		139	182	182
Provision for credit losses		3	0	12
Net Interest Income After Provision for Credit Losses		136	182	170
Noninterest income:
Service charges on deposits		1	1	1
Commercial banking revenue		2	1	2
Wealth and asset management revenue		498	469	429
Card and processing revenue		2	3	5
Mortgage banking net revenue		5	2	1
Leasing business revenue		0	0	0
Other noninterest income		18	13	18
Securities gains, net		0	0	0
Securities gains, net -non-qualifying hedges on MSRs		0	0	0
Total noninterest income		526	489	456
Noninterest expense:
Compensation and benefits		218	217	202
Technology and communications		1	1	1
Net occupancy expense		12	13	12
Leasing business expense		0	0	0
Equipment expense		1	1	1
Card and processing expense		1	1	0
Marketing expense		2	5	4
Other noninterest expense		298	291	284
Total noninterest expense		533	529	504
Income before income taxes		129	142	122
Applicable income tax expense		27	30	25
Net Income		102	112	97
General Corporate and Other
Segment Reporting Information
Total goodwill		0	0	0
Total assets		11,511	(11,669)	(8,982)
Net interest income		692	(441)	(26)
Provision for credit losses		(221)	15	8
Net Interest Income After Provision for Credit Losses		913	(456)	(34)
Noninterest income:
Service charges on deposits		0	(4)	0
Commercial banking revenue		(3)	0	(1)
Wealth and asset management revenue		0	0	0
Card and processing revenue		13	6	0
Mortgage banking net revenue		0	0	0
Leasing business revenue		0	0	0
Other noninterest income		14	863	651
Securities gains, net		62	40	(54)
Securities gains, net -non-qualifying hedges on MSRs		0	0	0
Total noninterest income		86	905	596
Noninterest expense:
Compensation and benefits		945	938	841
Technology and communications		336	398	267
Net occupancy expense		121	108	69
Leasing business expense		0	0	0
Equipment expense		61	55	49
Card and processing expense		(3)	(2)	(2)
Marketing expense		59	69	66
Other noninterest expense		(1,289)	(1,228)	(1,091)
Total noninterest expense		230	338	199
Income before income taxes		769	111	363
Applicable income tax expense		199	87	107
Net Income		570	24	256
Bank premises and equipment held for sale		35	27	42
Eliminations
Segment Reporting Information
Total goodwill		0	0	0
Total assets		0	0	0
Net interest income		0	0	0
Provision for credit losses		0	0	0
Net Interest Income After Provision for Credit Losses		0	0	0
Noninterest income:
Service charges on deposits		0	0	0
Commercial banking revenue		0	0	0
Wealth and asset management revenue		(153)	(143)	(138)
Card and processing revenue		0	0	0
Mortgage banking net revenue		0	0	0
Leasing business revenue		0	0	0
Other noninterest income		0	0	0
Securities gains, net		0	0	0
Securities gains, net -non-qualifying hedges on MSRs		0	0	0
Total noninterest income		(153)	(143)	(138)
Noninterest expense:
Compensation and benefits		0	0	0
Technology and communications		0	0	0
Net occupancy expense		0	0	0
Leasing business expense		0	0	0
Equipment expense		0	0	0
Card and processing expense		0	0	0
Marketing expense		0	0	0
Other noninterest expense		(153)	(143)	(138)
Total noninterest expense		(153)	(143)	(138)
Income before income taxes		0	0	0
Applicable income tax expense		0	0	0
Net Income		$ 0	$ 0	$ 0

[1] During the first quarter of 2020, certain noninterest income and noninterest expense line items were reclassified to better align disclosures to business activities. These reclassifications were retrospectively applied to all prior periods presented. Total noninterest income and noninterest expense did not change as a result of these reclassifications.