LHFI by Credit Quality Indicator (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 132,380	[1]	$ 133,112	[1]
Financing Receivable, Recorded Investment, Nonaccrual Status	612	[2],[3]	634	[2],[3]
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	65,574		65,440
Financing Receivable, Recorded Investment, Nonaccrual Status	140	[2]	151	[2]
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	6,389		6,741
Financing Receivable, Recorded Investment, Nonaccrual Status	24	[2]	21	[2]
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	6,389		6,741
Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	1,484		1,211
Financing Receivable, Recorded Investment, Nonaccrual Status	1	[2]	1	[2]
Residential Nonguaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	23,419	[4],[5]	23,443	[4],[5]
Financing Receivable, Recorded Investment, Nonaccrual Status	254	[2]	254	[2]
Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	13,954	[4]	14,264	[4]
Financing Receivable, Recorded Investment, Nonaccrual Status	165	[2]	174	[2]
Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	417	[4]	436	[4]
Financing Receivable, Recorded Investment, Nonaccrual Status	23	[2]	27	[2]
Consumer Other Direct [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	4,937	[6]	4,573	[6]
Financing Receivable, Recorded Investment, Nonaccrual Status	4	[2]	6	[2]
Consumer Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	10,336	[6]	10,644	[6]
Financing Receivable, Recorded Investment, Nonaccrual Status	1	[2]	0
Consumer Credit Card Financing Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	878	[6]	901	[6]
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	64,295		64,228
Pass | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	6,265		6,586
Pass | Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	1,468		1,196
Criticized Accruing | Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	1,139		1,061
Criticized Accruing | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	100		134
Criticized Accruing | Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	15		14
FICO Score 700 and Above [Member] | Residential Nonguaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	18,752	[4]	18,780	[4]
FICO Score 700 and Above [Member] | Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	11,245	[4]	11,475	[4]
FICO Score 700 and Above [Member] | Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	327	[4]	347	[4]
FICO Score 700 and Above [Member] | Consumer Other Direct [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	4,345	[6]	4,023	[6]
FICO Score 700 and Above [Member] | Consumer Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	7,324	[6]	7,661	[6]
FICO Score 700 and Above [Member] | Consumer Credit Card Financing Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	613	[6]	639	[6]
FICO Score Between 620 and 699 | Residential Nonguaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	3,411	[4]	3,369	[4]
FICO Score Between 620 and 699 | Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	1,932	[4]	1,991	[4]
FICO Score Between 620 and 699 | Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	71	[4]	70	[4]
FICO Score Between 620 and 699 | Consumer Other Direct [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	530	[6]	476	[6]
FICO Score Between 620 and 699 | Consumer Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	2,361	[6]	2,335	[6]
FICO Score Between 620 and 699 | Consumer Credit Card Financing Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	219	[6]	212	[6]
FICO Score Below 620 | Residential Nonguaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	1,256	[4],[7]	1,294	[4],[7]
FICO Score Below 620 | Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	777	[4],[7]	798	[4],[7]
FICO Score Below 620 | Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	19	[4],[7]	19	[4],[7]
FICO Score Below 620 | Consumer Other Direct [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	62	[6],[7]	74	[6],[7]
FICO Score Below 620 | Consumer Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	651	[6],[7]	648	[6],[7]
FICO Score Below 620 | Consumer Credit Card Financing Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 46	[6],[7]	$ 50	[6],[7]

[1] Includes loans of consolidated VIEs of $277 million and $288 million at March 31, 2015 and December 31, 2014, respectively.

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

[3] Nonaccruing loans past due 90 days or more totaled $379 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.

[4] Excludes $655 million and $632 million of guaranteed residential loans at March 31, 2015 and December 31, 2014, respectively.

[5] Includes $268 million of loans carried at fair value, the majority of which were accruing current.

[6] Excludes $4.3 billion and $4.8 billion of guaranteed student loans at March 31, 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.