Credit Quality (Summary of Transactions in the ALLL by Portfolio Segment) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance, Beginning of period	$ 1,103	$ 1,196	$ 1,253
Losses charged-off	(510)	(450)	(381)
Recoveries of losses previously charged-off	141	120	83
Provision for (benefit from) loan and lease losses	468	237	261
Deconsolidation of a VIE			(20)
Balance, end of period	1,202	1,103	1,196
Commercial Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance, Beginning of period	645	753	831
Losses charged-off	(127)	(157)	(154)
Recoveries of losses previously charged-off	19	25	29
Provision for (benefit from) loan and lease losses	173	24	66
Deconsolidation of a VIE			(19)
Balance, end of period	710	645	753
Residential Mortgage Loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance, Beginning of period	81	89	96
Losses charged-off	(9)	(13)	(15)
Recoveries of losses previously charged-off	5	6	8
Provision for (benefit from) loan and lease losses	(4)	(1)	0
Deconsolidation of a VIE			0
Balance, end of period	73	81	89
Consumer Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance, Beginning of period	267	234	214
Losses charged-off	(374)	(280)	(212)
Recoveries of losses previously charged-off	117	89	46
Provision for (benefit from) loan and lease losses	288	224	186
Deconsolidation of a VIE			0
Balance, end of period	298	267	234
Unallocated
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance, Beginning of period	110	120	112
Losses charged-off	0	0	0
Recoveries of losses previously charged-off	0	0	0
Provision for (benefit from) loan and lease losses	11	(10)	9
Deconsolidation of a VIE			(1)
Balance, end of period	$ 121	$ 110	$ 120