LHFI by Credit Quality Indicator (Detail) - USD ($) $ in Millions		Jun. 30, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[1]	$ 141,656	$ 136,442
Financing Receivable, Recorded Investment, Nonaccrual Status	[2],[3]	944	672
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		68,603	67,062
Financing Receivable, Recorded Investment, Nonaccrual Status		491	308
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		6,228	6,236
Financing Receivable, Recorded Investment, Nonaccrual Status		10	11
Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		2,617	1,954
Financing Receivable, Recorded Investment, Nonaccrual Status		2	0
Federal National Mortgage Association (FNMA) Insured Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		534	629
Financing Receivable, Recorded Investment, Nonaccrual Status		0	0
Residential Nonguaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[4],[5]	26,037	24,744
Financing Receivable, Recorded Investment, Nonaccrual Status		194	183
Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[4]	12,481	13,171
Financing Receivable, Recorded Investment, Nonaccrual Status		226	145
Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[4]	397	384
Financing Receivable, Recorded Investment, Nonaccrual Status		13	16
Federal Family Education Loan Program (FFELP) Guaranteed Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		5,562	4,922
Financing Receivable, Recorded Investment, Nonaccrual Status		0	0
Consumer Other Direct [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6]	6,825	6,127
Financing Receivable, Recorded Investment, Nonaccrual Status		5	6
Consumer Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6]	11,195	10,127
Financing Receivable, Recorded Investment, Nonaccrual Status		3	3
Credit Card Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6]	1,177	1,086
Financing Receivable, Recorded Investment, Nonaccrual Status		0	0
Pass | Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		66,234	65,379
Pass | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		5,933	6,067
Pass | Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		2,536	1,931
Criticized Accruing | Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		1,878	1,375
Criticized Accruing | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		285	158
Criticized Accruing | Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		79	23
FICO Score 700 and Above [Member] | Residential Nonguaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[4]	21,882	20,422
FICO Score 700 and Above [Member] | Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[4]	10,094	10,772
FICO Score 700 and Above [Member] | Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[4]	333	313
FICO Score 700 and Above [Member] | Consumer Other Direct [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6]	6,154	5,501
FICO Score 700 and Above [Member] | Consumer Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6]	7,834	7,015
FICO Score 700 and Above [Member] | Credit Card Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6]	827	759
FICO Score Between 620 and 699 | Residential Nonguaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[4]	3,174	3,262
FICO Score Between 620 and 699 | Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[4]	1,640	1,741
FICO Score Between 620 and 699 | Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[4]	53	58
FICO Score Between 620 and 699 | Consumer Other Direct [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6]	625	576
FICO Score Between 620 and 699 | Consumer Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6]	2,749	2,481
FICO Score Between 620 and 699 | Credit Card Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6]	285	265
FICO Score Below 620 | Residential Nonguaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[4],[7]	981	1,060
FICO Score Below 620 | Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[4],[7]	747	658
FICO Score Below 620 | Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[4],[7]	11	13
FICO Score Below 620 | Consumer Other Direct [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6],[7]	46	50
FICO Score Below 620 | Consumer Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6],[7]	612	631
FICO Score Below 620 | Credit Card Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6],[7]	$ 65	$ 62

[1] Includes loans of consolidated VIEs of $227 million and $246 million at June 30, 2016 and December 31, 2015, respectively.

[2] Nonaccruing loans past due 90 days or more totaled $305 million. Nonaccruing loans past due fewer than 90 days include modified nonaccrual loans reported as TDRs, performing second lien loans where the first lien loan is nonperforming, and certain energy-related commercial loans.

[3] Nonaccruing restructured loans are included in total nonaccrual/NPLs.

[4] Excludes $534 million and $629 million of guaranteed residential loans at June 30, 2016 and December 31, 2015, respectively.

[5] Includes $246 million of loans measured at fair value, the majority of which were accruing current.

[6] Excludes $5.6 billion and $4.9 billion of guaranteed student loans at June 30, 2016 and December 31, 2015, respectively.

[7] For substantially all loans with refreshed FICO scores below 620, the borrower’s FICO score at the time of origination exceeded 620 but has since deteriorated as the loan has seasoned.