LHFI by Credit Quality Indicator (Detail) - USD ($) $ in Millions		Mar. 31, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[1]	$ 139,746	$ 136,442
Financing Receivable, Recorded Investment, Nonaccrual Status	[2],[3]	975	672
Commercial and Industrial Sector [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		68,963	67,062
Financing Receivable, Recorded Investment, Nonaccrual Status		565	308
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		6,034	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		2,498	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		623	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]	25,148	24,744
Financing Receivable, Recorded Investment, Nonaccrual Status		198	183
Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[4]	12,845	13,171
Financing Receivable, Recorded Investment, Nonaccrual Status		180	145
Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[4]	383	384
Financing Receivable, Recorded Investment, Nonaccrual Status		12	16
Federal Family Education Loan Program (FFELP) Guaranteed Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		5,265	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]	6,372	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]	10,522	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]	1,093	1,086
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		66,633	65,379
Pass | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		5,744	6,067
Pass | Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		2,459	1,931
Criticized Accruing | Commercial and Industrial Sector [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		1,765	1,375
Criticized Accruing | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		280	158
Criticized Accruing | Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		37	23
FICO Score 700 and Above [Member] | Residential Nonguaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[4]	20,846	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]	10,476	10,772
FICO Score 700 and Above [Member] | Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[4]	322	313
FICO Score 700 and Above [Member] | Consumer Other Direct [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6]	5,731	5,501
FICO Score 700 and Above [Member] | Consumer Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6]	7,267	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]	761	759
FICO Score Between 620 and 699 | Residential Nonguaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[4]	3,249	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]	1,717	1,741
FICO Score Between 620 and 699 | Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[4]	49	58
FICO Score Between 620 and 699 | Consumer Other Direct [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6]	591	576
FICO Score Between 620 and 699 | Consumer Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6]	2,565	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]	268	265
FICO Score Below 620 | Residential Nonguaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[4],[7]	1,053	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]	652	658
FICO Score Below 620 | Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[4],[7]	12	13
FICO Score Below 620 | Consumer Other Direct [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6],[7]	50	50
FICO Score Below 620 | Consumer Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6],[7]	690	631
FICO Score Below 620 | Credit Card Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6],[7]	$ 64	$ 62

[1] Includes loans of consolidated VIEs of $237 million and $246 million at March 31, 2016 and December 31, 2015, respectively.

[2] Nonaccruing loans past due 90 days or more totaled $332 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 $623 million and $629 million of guaranteed residential loans at March 31, 2016 and December 31, 2015, respectively.

[5] Includes $255 million of loans measured at fair value, the majority of which were accruing current.

[6] Excludes $5.3 billion and $4.9 billion of guaranteed student loans at March 31, 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.