LHFI by Credit Quality Indicator (Detail) - USD ($) $ in Millions		Sep. 30, 2015	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[1]	$ 133,560	$ 133,112
Financing Receivable, Recorded Investment, Nonaccrual Status	[2],[3]	463	634
Commercial and Industrial Sector [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		65,371	65,440
Financing Receivable, Recorded Investment, Nonaccrual Status		122	151
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		6,168	6,741
Financing Receivable, Recorded Investment, Nonaccrual Status		15	21
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		6,168	6,741
Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		1,763	1,211
Financing Receivable, Recorded Investment, Nonaccrual Status		1	1
Federal National Mortgage Association (FNMA) Insured Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		627	632
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]	24,351	23,443
Financing Receivable, Recorded Investment, Nonaccrual Status		156	254
Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[4]	13,416	14,264
Financing Receivable, Recorded Investment, Nonaccrual Status		146	174
Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[4]	394	436
Financing Receivable, Recorded Investment, Nonaccrual Status		16	27
Federal Family Education Loan Program (FFELP) Guaranteed Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		4,588	4,827
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]	5,771	4,573
Financing Receivable, Recorded Investment, Nonaccrual Status		4	6
Consumer Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6]	10,119	10,644
Financing Receivable, Recorded Investment, Nonaccrual Status		3	0
Credit Card Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6]	992	901
Financing Receivable, Recorded Investment, Nonaccrual Status		0	0
Pass | Commercial and Industrial Sector [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		63,826	64,228
Pass | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		6,033	6,586
Pass | Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		1,739	1,196
Criticized Accruing | Commercial and Industrial Sector [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		1,423	1,061
Criticized Accruing | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		120	134
Criticized Accruing | Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		23	14
FICO Score 700 and Above [Member] | Residential Nonguaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[4]	19,936	18,780
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]	10,897	11,475
FICO Score 700 and Above [Member] | Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[4]	321	347
FICO Score 700 and Above [Member] | Consumer Other Direct [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6]	5,180	4,023
FICO Score 700 and Above [Member] | Consumer Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6]	7,053	7,661
FICO Score 700 and Above [Member] | Credit Card Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6]	690	639
FICO Score Between 620 and 699 | Residential Nonguaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[4]	3,330	3,369
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]	1,827	1,991
FICO Score Between 620 and 699 | Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[4]	59	70
FICO Score Between 620 and 699 | Consumer Other Direct [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6]	536	476
FICO Score Between 620 and 699 | Consumer Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6]	2,426	2,335
FICO Score Between 620 and 699 | Credit Card Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6]	245	212
FICO Score Below 620 | Residential Nonguaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[4],[7]	1,085	1,294
FICO Score Below 620 | Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[4],[7]	692	798
FICO Score Below 620 | Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[4],[7]	14	19
FICO Score Below 620 | Consumer Other Direct [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6],[7]	55	74
FICO Score Below 620 | Consumer Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6],[7]	640	648
FICO Score Below 620 | Credit Card Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6],[7]	$ 57	$ 50

[1] Includes loans of consolidated VIEs of $256 million and $288 million at September 30, 2015 and December 31, 2014, respectively.

[2] Nonaccruing loans past due 90 days or more totaled $278 million. Nonaccruing loans past due fewer than 90 days include modified nonaccrual loans reported as TDRs and performing second lien loans which are classified as nonaccrual when the first lien loan is nonperforming.

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

[4] Excludes $627 million and $632 million of guaranteed residential loans at September 30, 2015 and December 31, 2014, respectively.

[5] Includes $262 million of loans measured at fair value, the majority of which were accruing current.

[6] Excludes $4.6 billion and $4.8 billion of guaranteed student loans at September 30, 2015 and December 31, 2014, 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.