Segments - Results of Operations and Average Assets by Segment (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Net interest income	$ 1,242	$ 1,043		$ 3,569	$ 3,059
Provision for (benefit from) credit losses	134	84		310	111
Net interest income after provision for credit losses	1,108	959		3,259	2,948
Noninterest Income
Service charges on deposits	143	139		417	414
Wealth and asset management revenue	124	114		358	335
Corporate banking revenue	168	100		417	308
Card and processing revenue	94	82		266	245
Mortgage banking net revenue	95	49		214	158
Other noninterest income	111	86		794	794
Securities gains (losses), net	5	(6)		30	(21)
Securities gains (losses), net - non-qualifying hedges on mortgage servcing rights	0	(1)		5	(18)
Total noninterest income	740	563		2,501	2,215
Noninterest Expense
Salaries, wages and incentives	497	421		1,527	1,339
Employee benefits	87	82		316	270
Net occupancy expense	84	70		248	219
Technology and communications	100	71		319	206
Equipment expense	33	31		96	92
Card and processing expense	33	31		98	91
Other noninterest expense	325	266		895	767
Total noninterest expense	1,159	972		3,499	2,984
Income (Loss) Before Income Taxes	689	550		2,261	2,179
Applicable income tax expense	140	114		483	442
Net income (loss)	549	436	$ 1,778	1,778	1,737	$ 1,737
Goodwill	4,290	2,462	4,290	4,290	2,462	2,462	$ 2,478	$ 2,445
Total Assets	171,079	141,590	171,079	171,079	141,590	141,590	146,069
Intersegment Elimination
Segment Reporting Information [Line Items]
Net interest income	0	0		0	0
Provision for (benefit from) credit losses	0	0		0	0
Net interest income after provision for credit losses	0	0		0	0
Noninterest Income
Service charges on deposits	0	0		0	0
Wealth and asset management revenue	(37)	(35)		(106)	(104)
Corporate banking revenue	0	0		0	0
Card and processing revenue	0	0		0	0
Mortgage banking net revenue	0	0		0	0
Other noninterest income	0	0		0	0
Securities gains (losses), net	0	0		0	0
Securities gains (losses), net - non-qualifying hedges on mortgage servcing rights	0	0		0	0
Total noninterest income	(37)	(35)		(106)	(104)
Noninterest Expense
Salaries, wages and incentives	0	0		0	0
Employee benefits	0	0		0	0
Net occupancy expense	0	0		0	0
Technology and communications	0	0		0	0
Equipment expense	0	0		0	0
Card and processing expense	0	0		0	0
Other noninterest expense	(37)	(35)		(106)	(104)
Total noninterest expense	(37)	(35)		(106)	(104)
Income (Loss) Before Income Taxes	0	0		0	0
Applicable income tax expense	0	0		0	0
Net income (loss)	0	0		0	0
Goodwill	0	0	0	0	0	0
Total Assets	0	0	0	0	0	0
Branch Banking
Segment Reporting Information [Line Items]
Net interest income	598	525		1,802	1,490
Provision for (benefit from) credit losses	58	34		164	124
Net interest income after provision for credit losses	540	491		1,638	1,366
Noninterest Income
Service charges on deposits	65	71		191	205
Wealth and asset management revenue	41	38		117	113
Corporate banking revenue	1	1		3	4
Card and processing revenue	74	67		212	199
Mortgage banking net revenue	2	1		4	4
Other noninterest income	21	26		63	33
Securities gains (losses), net	0	0		0	0
Securities gains (losses), net - non-qualifying hedges on mortgage servcing rights	0	0		0	0
Total noninterest income	204	204		590	558
Noninterest Expense
Salaries, wages and incentives	122	109		360	329
Employee benefits	26	22		84	75
Net occupancy expense	44	44		130	131
Technology and communications	1	1		3	4
Equipment expense	12	12		35	37
Card and processing expense	32	30		92	89
Other noninterest expense	232	215		671	638
Total noninterest expense	469	433		1,375	1,303
Income (Loss) Before Income Taxes	275	262		853	621
Applicable income tax expense	58	55		179	131
Net income (loss)	217	207		674	490
Goodwill	2,054	1,655	2,054	2,054	1,655	1,655	1,655	1,655
Total Assets	69,021	60,222	69,021	69,021	60,222	60,222
Commercial Banking
Segment Reporting Information [Line Items]
Net interest income	623	427		1,761	1,273
Provision for (benefit from) credit losses	54	(11)		100	(41)
Net interest income after provision for credit losses	569	438		1,661	1,314
Noninterest Income
Service charges on deposits	79	68		227	207
Wealth and asset management revenue	1	1		2	3
Corporate banking revenue	167	100		413	304
Card and processing revenue	16	14		49	42
Mortgage banking net revenue	0	0		0	0
Other noninterest income	72	52		170	125
Securities gains (losses), net	0	0		0	0
Securities gains (losses), net - non-qualifying hedges on mortgage servcing rights	0	0		0	0
Total noninterest income	335	235		861	681
Noninterest Expense
Salaries, wages and incentives	107	71		299	214
Employee benefits	11	8		47	36
Net occupancy expense	7	6		21	20
Technology and communications	3	2		8	6
Equipment expense	7	6		18	18
Card and processing expense	2	2		6	3
Other noninterest expense	288	212		799	652
Total noninterest expense	425	307		1,198	949
Income (Loss) Before Income Taxes	479	366		1,324	1,046
Applicable income tax expense	86	65		242	184
Net income (loss)	393	301		1,082	862
Goodwill	1,982	630	1,982	1,982	630	630	630	613
Total Assets	75,143	60,040	75,143	75,143	60,040	60,040
Consumer Lending
Segment Reporting Information [Line Items]
Net interest income	88	60		234	178
Provision for (benefit from) credit losses	14	10		34	30
Net interest income after provision for credit losses	74	50		200	148
Noninterest Income
Service charges on deposits	0	0		0	0
Wealth and asset management revenue	0	0		0	0
Corporate banking revenue	0	0		0	0
Card and processing revenue	0	0		0	0
Mortgage banking net revenue	92	48		209	153
Other noninterest income	4	3		10	11
Securities gains (losses), net	0	0		0	0
Securities gains (losses), net - non-qualifying hedges on mortgage servcing rights	0	(1)		5	(18)
Total noninterest income	96	50		224	146
Noninterest Expense
Salaries, wages and incentives	39	38		117	120
Employee benefits	9	8		29	28
Net occupancy expense	3	3		8	8
Technology and communications	2	2		6	3
Equipment expense	0	0		0	0
Card and processing expense	0	0		0	0
Other noninterest expense	61	49		175	151
Total noninterest expense	114	100		335	310
Income (Loss) Before Income Taxes	56	0		89	(16)
Applicable income tax expense	12	0		19	(3)
Net income (loss)	44	0		70	(13)
Goodwill	0	0	0	0	0	0	0	0
Total Assets	26,171	22,188	26,171	26,171	22,188	22,188
Wealth and Asset Management
Segment Reporting Information [Line Items]
Net interest income	44	46		141	134
Provision for (benefit from) credit losses	0	3		0	8
Net interest income after provision for credit losses	44	43		141	126
Noninterest Income
Service charges on deposits	0	0		1	1
Wealth and asset management revenue	119	110		345	324
Corporate banking revenue	0	0		1	1
Card and processing revenue	1	1		2	4
Mortgage banking net revenue	1	0		1	1
Other noninterest income	4	4		9	13
Securities gains (losses), net	0	0		0	0
Securities gains (losses), net - non-qualifying hedges on mortgage servcing rights	0	0		0	0
Total noninterest income	125	115		359	344
Noninterest Expense
Salaries, wages and incentives	45	44		140	131
Employee benefits	6	6		25	23
Net occupancy expense	3	3		10	9
Technology and communications	0	0		1	1
Equipment expense	0	0		1	0
Card and processing expense	0	0		1	0
Other noninterest expense	75	73		219	217
Total noninterest expense	129	126		397	381
Income (Loss) Before Income Taxes	40	32		103	89
Applicable income tax expense	8	7		22	19
Net income (loss)	32	25		81	70
Goodwill	254	177	254	254	177	177	193	177
Total Assets	9,961	9,171	9,961	9,961	9,171	9,171
General Corporate and Other
Segment Reporting Information [Line Items]
Net interest income	(111)	(15)		(369)	(16)
Provision for (benefit from) credit losses	8	48		12	(10)
Net interest income after provision for credit losses	(119)	(63)		(381)	(6)
Noninterest Income
Service charges on deposits	(1)	0		(2)	1
Wealth and asset management revenue	0	0		0	(1)
Corporate banking revenue	0	(1)		0	(1)
Card and processing revenue	3	0		3	0
Mortgage banking net revenue	0	0		0	0
Other noninterest income	10	1		542	612
Securities gains (losses), net	5	(6)		30	(21)
Securities gains (losses), net - non-qualifying hedges on mortgage servcing rights	0	0		0	0
Total noninterest income	17	(6)		573	590
Noninterest Expense
Salaries, wages and incentives	184	159		611	545
Employee benefits	35	38		131	108
Net occupancy expense	27	14		79	51
Technology and communications	94	66		301	192
Equipment expense	14	13		42	37
Card and processing expense	(1)	(1)		(1)	(1)
Other noninterest expense	(294)	(248)		(863)	(787)
Total noninterest expense	59	41		300	145
Income (Loss) Before Income Taxes	(161)	(110)		(108)	439
Applicable income tax expense	(24)	(13)		21	111
Net income (loss)	(137)	(97)		(129)	328
Goodwill	0	0	0	0	0	0	$ 0	$ 0
Total Assets	$ (9,217)	$ (10,031)	$ (9,217)	$ (9,217)	$ (10,031)	$ (10,031)