Segments - Results of Operations and Average Assets by Segment (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Net interest income	$ 1,245	$ 1,020		$ 2,327		$ 2,016
Provision for (benefit from) credit losses	85	14		175		27
Net interest income after provision for credit losses	1,160	1,006		2,152		1,989
Noninterest Income
Service charges on deposits	143	137		274		275
Wealth and asset management revenue	122	108		234		221
Corporate banking revenue	137	120		249		208
Card and processing revenue	92	84		171		163
Mortgage banking net revenue	63	53		119		109
Other noninterest income	93	250		684		708
Securities gains (losses), net	8	(5)		25		(15)
Securities gains (losses), net - non-qualifying hedges on mortgage servcing rights	2	(4)		5		(17)
Total noninterest income	660	743		1,761		1,652
Noninterest Expense
Salaries, wages and incentives	544	471		1,023		918
Employee benefits	97	78		228		188
Net occupancy expense	88	74		164		149
Technology and communications	136	67		219		135
Equipment expense	33	30		63		61
Card and processing expense	34	30		64		60
Other noninterest expense	311	251		580		500
Total noninterest expense	1,243	1,001		2,341		2,011
Income (Loss) Before Income Taxes	577	748		1,572		1,630
Applicable income tax expense	124	146		344		327
Net income (loss)	453	602	$ 1,228	1,228	$ 1,303	1,303
Goodwill	4,284	2,462	4,284	4,284	2,462	2,462	$ 2,478	$ 2,445
Total Assets	168,802	140,595	168,802	168,802	140,595	140,595	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	(36)	(34)		(69)		(69)
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	(36)	(34)		(69)		(69)
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	(36)	(34)		(69)		(69)
Total noninterest expense	(36)	(34)		(69)		(69)
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	620	499		1,204		965
Provision for (benefit from) credit losses	55	47		107		90
Net interest income after provision for credit losses	565	452		1,097		875
Noninterest Income
Service charges on deposits	63	67		127		134
Wealth and asset management revenue	40	37		76		74
Corporate banking revenue	1	1		2		2
Card and processing revenue	73	69		137		133
Mortgage banking net revenue	1	1		2		3
Other noninterest income	24	(8)		42		7
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	202	167		386		353
Noninterest Expense
Salaries, wages and incentives	123	111		237		220
Employee benefits	29	26		58		53
Net occupancy expense	43	44		86		88
Technology and communications	1	1		2		3
Equipment expense	12	12		24		25
Card and processing expense	32	30		61		59
Other noninterest expense	227	208		439		423
Total noninterest expense	467	432		907		871
Income (Loss) Before Income Taxes	300	187		576		357
Applicable income tax expense	63	40		121		75
Net income (loss)	237	147		455		282
Goodwill	1,655	1,655	1,655	1,655	1,655	1,655	1,655	1,655
Total Assets	69,577	60,281	69,577	69,577	60,281	60,281
Commercial Banking
Segment Reporting Information [Line Items]
Net interest income	629	427		1,138		846
Provision for (benefit from) credit losses	25	(10)		46		(29)
Net interest income after provision for credit losses	604	437		1,092		875
Noninterest Income
Service charges on deposits	82	70		149		139
Wealth and asset management revenue	1	1		1		2
Corporate banking revenue	135	119		247		205
Card and processing revenue	18	14		32		28
Mortgage banking net revenue	0	0		0		0
Other noninterest income	65	25		98		73
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	301	229		527		447
Noninterest Expense
Salaries, wages and incentives	105	71		191		141
Employee benefits	14	9		36		27
Net occupancy expense	7	6		14		13
Technology and communications	3	2		5		4
Equipment expense	6	6		12		11
Card and processing expense	2	1		4		2
Other noninterest expense	283	208		514		444
Total noninterest expense	420	303		776		642
Income (Loss) Before Income Taxes	485	363		843		680
Applicable income tax expense	90	58		156		120
Net income (loss)	395	305		687		560
Goodwill	630	630	630	630	630	630	630	613
Total Assets	74,033	58,663	74,033	74,033	58,663	58,663
Consumer Lending
Segment Reporting Information [Line Items]
Net interest income	83	59		146		118
Provision for (benefit from) credit losses	7	8		20		20
Net interest income after provision for credit losses	76	51		126		98
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	62	52		117		106
Other noninterest income	3	4		7		7
Securities gains (losses), net	0	0		0		0
Securities gains (losses), net - non-qualifying hedges on mortgage servcing rights	2	(4)		5		(17)
Total noninterest income	67	52		129		96
Noninterest Expense
Salaries, wages and incentives	42	42		77		82
Employee benefits	10	10		20		20
Net occupancy expense	3	3		5		5
Technology and communications	2	1		4		2
Equipment expense	0	0		0		0
Card and processing expense	0	0		0		0
Other noninterest expense	61	51		114		102
Total noninterest expense	118	107		220		211
Income (Loss) Before Income Taxes	25	(4)		35		(17)
Applicable income tax expense	5	(1)		7		(3)
Net income (loss)	20	(3)		28		(14)
Goodwill	0	0	0	0	0	0	0	0
Total Assets	25,506	22,128	25,506	25,506	22,128	22,128
Wealth and Asset Management
Segment Reporting Information [Line Items]
Net interest income	48	45		97		88
Provision for (benefit from) credit losses	0	(11)		0		5
Net interest income after provision for credit losses	48	56		97		83
Noninterest Income
Service charges on deposits	0	0		0		1
Wealth and asset management revenue	117	104		226		214
Corporate banking revenue	0	0		0		1
Card and processing revenue	1	1		2		2
Mortgage banking net revenue	0	0		0		0
Other noninterest income	0	4		5		9
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	118	109		233		227
Noninterest Expense
Salaries, wages and incentives	49	43		94		87
Employee benefits	8	7		19		17
Net occupancy expense	3	3		7		6
Technology and communications	0	0		1		0
Equipment expense	0	0		0		0
Card and processing expense	0	0		0		0
Other noninterest expense	75	70		146		144
Total noninterest expense	135	123		267		254
Income (Loss) Before Income Taxes	31	42		63		56
Applicable income tax expense	7	9		14		12
Net income (loss)	24	33		49		44
Goodwill	190	177	190	190	177	177	193	177
Total Assets	9,841	9,270	9,841	9,841	9,270	9,270
General Corporate and Other
Segment Reporting Information [Line Items]
Net interest income	(135)	(10)		(258)		(1)
Provision for (benefit from) credit losses	(2)	(20)		2		(59)
Net interest income after provision for credit losses	(133)	10		(260)		58
Noninterest Income
Service charges on deposits	(2)	0		(2)		1
Wealth and asset management revenue	0	0		0		0
Corporate banking revenue	1	0		0		0
Card and processing revenue	0	0		0		0
Mortgage banking net revenue	0	0		0		0
Other noninterest income	1	225		532		612
Securities gains (losses), net	8	(5)		25		(15)
Securities gains (losses), net - non-qualifying hedges on mortgage servcing rights	0	0		0		0
Total noninterest income	8	220		555		598
Noninterest Expense
Salaries, wages and incentives	225	204		424		388
Employee benefits	36	26		95		71
Net occupancy expense	32	18		52		37
Technology and communications	130	63		207		126
Equipment expense	15	12		27		25
Card and processing expense	0	(1)		(1)		(1)
Other noninterest expense	(299)	(252)		(564)		(544)
Total noninterest expense	139	70		240		102
Income (Loss) Before Income Taxes	(264)	160		55		554
Applicable income tax expense	(41)	40		46		123
Net income (loss)	(223)	120		9		431
Goodwill	1,809	0	1,809	1,809	0	0	$ 0	$ 0
Total Assets	$ (10,155)	$ (9,747)	$ (10,155)	$ (10,155)	$ (9,747)	$ (9,747)