LHFI Considered Impaired (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance		$ 3,039		$ 3,046
Impaired Financing Receivable, Recorded Investment	[1]	2,812		2,821
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		196		204
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		2,825	$ 3,116
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	[2]	30	32
Commercial and Industrial [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance		28		38
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	[1]	20		35
Impaired Financing Receivable, Unpaid Principal Balance		157		127
Impaired Financing Receivable, Recorded Investment	[1]	149		117
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		22		19
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment		20	240
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	[2]	0	1
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		149	165
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	[2]	1	1
Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance		21		0
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	[1]	21		0
Impaired Financing Receivable, Unpaid Principal Balance		25		21
Impaired Financing Receivable, Recorded Investment	[1]	21		21
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		0		2
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment		21	0
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method		0	0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		25	17
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	[2]	0	0
Commercial Portfolio Segment [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance		49		38
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	[1]	41		35
Impaired Financing Receivable, Unpaid Principal Balance		182		148
Impaired Financing Receivable, Recorded Investment	[1]	170		138
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		22		21
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment		41	240
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	[2]	0	1
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		174	182
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	[2]	1	1
Residential Nonguaranteed [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance		453		458
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	[1]	355		363
Impaired Financing Receivable, Unpaid Principal Balance		1,112		1,133
Impaired Financing Receivable, Recorded Investment	[1]	1,087		1,103
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		107		113
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment		353	360
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	[2]	4	4
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		1,093	1,216
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	[2]	12	15
Home Equity Line of Credit [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance		927		953
Impaired Financing Receivable, Recorded Investment	[1]	871		895
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		52		54
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		873	833
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	[2]	9	8
Residential Construction [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance		12		15
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	[1]	6		9
Impaired Financing Receivable, Unpaid Principal Balance		91		93
Impaired Financing Receivable, Recorded Investment	[1]	89		90
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		7		7
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment		6	8
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	[2]	0	0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		90	105
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	[2]	1	1
Consumer Other Direct [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance		57		59
Impaired Financing Receivable, Recorded Investment	[1]	58		59
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		1		1
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		57	58
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	[2]	1	1
Consumer Indirect [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance		129		123
Impaired Financing Receivable, Recorded Investment	[1]	128		122
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		6		7
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		131	108
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	[2]	2	1
Credit Card Receivable [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance		27		26
Impaired Financing Receivable, Recorded Investment	[1]	7		7
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		1		1
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		7	6
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	[2]	0	0
Consumer Portfolio Segment [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance		465		473
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	[1]	361		372
Impaired Financing Receivable, Unpaid Principal Balance		2,343		2,387
Impaired Financing Receivable, Recorded Investment	[1]	2,240		2,276
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		174		$ 183
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment		359	368
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	[2]	4	4
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		2,251	2,326
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	[2]	$ 25	$ 26

[1] Carrying value reflects charge-offs that have been recognized plus other amounts that have been applied to adjust the net book balance.

[2] Of the interest income recognized during each of the three months ended March 31, 2018 and 2017, cash basis interest income was less than $1 million.