LHFI Considered Impaired (Detail) - USD ($)		12 Months Ended
		Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance		$ 3,046,000,000		$ 3,434,000,000
Impaired Financing Receivable, Recorded Investment	[1]	2,821,000,000		3,068,000,000
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		204,000,000		255,000,000
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		2,866,000,000		3,045,000,000		$ 2,916,000,000
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method		125,000,000	[2]	128,000,000	[2]	132,000,000
Commercial and Industrial [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance		38,000,000		266,000,000
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	[1]	35,000,000		214,000,000
Impaired Financing Receivable, Unpaid Principal Balance		127,000,000		225,000,000
Impaired Financing Receivable, Recorded Investment	[1]	117,000,000		151,000,000
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		19,000,000		31,000,000
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment		34,000,000		169,000,000		58,000,000
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method		1,000,000	[2]	3,000,000	[2]	2,000,000
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		112,000,000		170,000,000		147,000,000
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method		2,000,000	[2]	1,000,000	[2]	5,000,000
Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance		21,000,000		26,000,000
Impaired Financing Receivable, Recorded Investment	[1]	21,000,000		17,000,000
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		2,000,000		2,000,000
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment		0		0		10,000,000
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method		0		0		0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		22,000,000		25,000,000		0
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method		1,000,000	[2]	1,000,000	[2]	0
Commercial Portfolio Segment [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance		38,000,000		266,000,000
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	[1]	35,000,000		214,000,000
Impaired Financing Receivable, Unpaid Principal Balance		148,000,000		251,000,000
Impaired Financing Receivable, Recorded Investment	[1]	138,000,000		168,000,000
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		21,000,000		33,000,000
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment		34,000,000		169,000,000		68,000,000
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method		1,000,000	[2]	3,000,000	[2]	2,000,000
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		134,000,000		195,000,000		147,000,000
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method		3,000,000	[2]	2,000,000	[2]	5,000,000
Residential Nonguaranteed [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance		458,000,000		466,000,000
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	[1]	363,000,000		360,000,000
Impaired Financing Receivable, Unpaid Principal Balance		1,133,000,000		1,277,000,000
Impaired Financing Receivable, Recorded Investment	[1]	1,103,000,000		1,248,000,000
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		113,000,000		150,000,000
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment		357,000,000		370,000,000		390,000,000
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method		15,000,000	[2]	16,000,000	[2]	17,000,000
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		1,123,000,000		1,251,000,000		1,349,000,000
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method		58,000,000	[2]	64,000,000	[2]	65,000,000
Home Equity Line of Credit [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance		953,000,000		863,000,000
Impaired Financing Receivable, Recorded Investment	[1]	895,000,000		795,000,000
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		54,000,000		54,000,000
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		914,000,000		812,000,000		682,000,000
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method		32,000,000	[2]	29,000,000	[2]	28,000,000
Residential Construction [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance		15,000,000		16,000,000
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	[1]	9,000,000		8,000,000
Impaired Financing Receivable, Unpaid Principal Balance		93,000,000		109,000,000
Impaired Financing Receivable, Recorded Investment	[1]	90,000,000		107,000,000
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		7,000,000		11,000,000
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment		8,000,000		8,000,000		11,000,000
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method		0	[2]	0	[2]	0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		94,000,000		110,000,000		125,000,000
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method		5,000,000	[2]	6,000,000	[2]	8,000,000
Consumer Other Direct [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance		59,000,000		59,000,000	[3]
Impaired Financing Receivable, Recorded Investment	[1]	59,000,000		59,000,000	[3]
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		1,000,000		1,000,000
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		60,000,000		10,000,000		12,000,000
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method		4,000,000	[2]	1,000,000	[2]	0
Consumer Indirect [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance		123,000,000		103,000,000
Impaired Financing Receivable, Recorded Investment	[1]	122,000,000		103,000,000
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		7,000,000		5,000,000
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		136,000,000		114,000,000		125,000,000
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method		6,000,000	[2]	6,000,000	[2]	6,000,000
Credit Card Receivable [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance		26,000,000		24,000,000
Impaired Financing Receivable, Recorded Investment	[1]	7,000,000		6,000,000
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		1,000,000		1,000,000
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		6,000,000		6,000,000		7,000,000
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method		1,000,000	[2]	1,000,000	[2]	1,000,000
Consumer Portfolio Segment [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance		473,000,000		482,000,000
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	[1]	372,000,000		368,000,000
Impaired Financing Receivable, Unpaid Principal Balance		2,387,000,000		2,435,000,000
Impaired Financing Receivable, Recorded Investment	[1]	2,276,000,000		2,318,000,000
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		183,000,000		222,000,000
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment		365,000,000		378,000,000		401,000,000
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method		15,000,000	[2]	16,000,000	[2]	17,000,000
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		2,333,000,000		2,303,000,000		2,300,000,000
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method		$ 106,000,000	[2]	$ 107,000,000	[2]	$ 108,000,000

[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 the years ended December 31, 2017, 2016, and 2015, cash basis interest income was $4 million, $4 million, and $7 million, respectively.

[3] Includes $41 million of TDRs that were modified prior to 2016 and reclassified as TDRs in the fourth quarter of 2016.