Credit Quality - Summary of Transactions in the ALLL by Portfolio Segment (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance, beginning of period	$ 1,115	$ 1,077	$ 1,103	$ 1,196
Losses charged-off	(130)	(112)	(358)	(334)
Recoveries of losses previously charged- off	31	40	102	87
Provision for (benefit from) loan and lease losses	127	86	296	142
Balance, end of period	1,143	1,091	1,143	1,091
Commercial Portfolio Segment
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance, beginning of period	651	654	645	753
Losses charged-off	(34)	(36)	(87)	(124)
Recoveries of losses previously charged- off	1	9	14	19
Provision for (benefit from) loan and lease losses	53	29	99	8
Balance, end of period	671	656	671	656
Residential Mortgage Loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance, beginning of period	76	86	81	89
Losses charged-off	(2)	(3)	(5)	(10)
Recoveries of losses previously charged- off	1	1	4	4
Provision for (benefit from) loan and lease losses	0	(1)	(5)	0
Balance, end of period	75	83	75	83
Consumer Portfolio Segment
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance, beginning of period	276	229	267	234
Losses charged-off	(94)	(73)	(266)	(200)
Recoveries of losses previously charged- off	29	30	84	64
Provision for (benefit from) loan and lease losses	72	57	198	145
Balance, end of period	283	243	283	243
Unallocated
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance, beginning of period	112	108	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	2	1	4	(11)
Balance, end of period	$ 114	$ 109	$ 114	$ 109