Credit Quality - Summary of Transactions in the ALLL by Portfolio Segment (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance, beginning of period	$ 1,115	$ 1,138	$ 1,103	$ 1,196
Losses charged-off	(119)	(118)	(228)	(222)
Recoveries of losses previously charged- off	41	24	72	47
Provision for (benefit from) loan and lease losses	78	33	168	56
Balance, end of period	1,115	1,077	1,115	1,077
Commercial Portfolio Segment
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance, beginning of period	654	713	645	753
Losses charged-off	(33)	(54)	(53)	(87)
Recoveries of losses previously charged- off	10	5	13	11
Provision for (benefit from) loan and lease losses	20	(10)	46	(23)
Balance, end of period	651	654	651	654
Residential Mortgage Loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance, beginning of period	79	89	81	89
Losses charged-off	(1)	(4)	(3)	(7)
Recoveries of losses previously charged- off	2	2	3	3
Provision for (benefit from) loan and lease losses	(4)	(1)	(5)	1
Balance, end of period	76	86	76	86
Consumer Portfolio Segment
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance, beginning of period	270	222	267	234
Losses charged-off	(85)	(60)	(172)	(128)
Recoveries of losses previously charged- off	29	17	56	33
Provision for (benefit from) loan and lease losses	62	50	125	90
Balance, end of period	276	229	276	229
Unallocated
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance, beginning of period	112	114	110	120
Losses charged-off	0	0	0	0
Recoveries of losses previously charged- off	0	0	0	0
Provision for (benefit from) loan and lease losses	0	(6)	2	(12)
Balance, end of period	$ 112	$ 108	$ 112	$ 108