Summary of the ALLL and Related Loans and Leases Classified by Portfolio Segment (Parenthetical) (Detail) $ in Millions	9 Months Ended				12 Months Ended
	Sep. 30, 2015 USD ($) number		Sep. 30, 2014 USD ($)		Dec. 31, 2014 USD ($) number		Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Dec. 31, 2013 USD ($)
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan and lease losses	$ 1,261	[1]	$ 1,414		$ 1,322	[1]	$ 1,293	$ 1,458	$ 1,582
Portfolio loans and leases	$ 93,401	[2]			89,976	[3]
Number of Contracts	11,227	[4],[5]	6,916	[6],[7]
Recorded Investment	$ 1,916	[8]			2,233	[9]
Variable Interest Entity, Primary Beneficiary
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan and lease losses	27				22
Commercial | Variable Interest Entity, Primary Beneficiary
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan and lease losses	$ 15				$ 10
Number of Contracts | number	5				5
Recorded Investment	$ 28				$ 28
Leveraged Leases
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan and lease losses	5				6
Portfolio loans and leases	854				874
Residential Mortgage Loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Portfolio loans and leases at fair value	$ 173				$ 108

[1] Includes $137 and $179 of cash and due from banks, $2,179 and $3,378 of portfolio loans and leases, $(27) and $(22) of ALLL, $18 and $25 of other assets, $3 and $5 of other liabilities, and $2,136 and $3,434 of long-term debt from consolidated VIEs that are included in their respective captions above at September 30, 2015 and December 31, 2014, respectively. For further information refer to Note 11.

[2] Excludes $173 of residential mortgage loans measured at fair value.

[3] Excludes $108 of residential mortgage loans measured at fair value.

[4] Excludes all loans and leases held for sale and loans acquired with deteriorated credit quality which were accounted for within a pool.

[5] Represents number of loans post-modification and excludes loans previously modified in a TDR.

[6] Excludes all loans and leases held for sale and loans acquired with deteriorated credit quality which were accounted for within a pool.

[7] Represents number of loans post-modification and excludes loans previously modified in a TDR.

[8] Includes $571, $589 and $384, respectively, of commercial, residential mortgage and consumer TDRs on accrual status and $177, $24 and $52, respectively, of commercial, residential mortgage and consumer TDRs on nonaccrual status at September 30, 2015.

[9] Includes $869, $485 and $420, respectively, of commercial, residential mortgage and consumer TDRs on accrual status and $214, $33 and $63, respectively, of commercial, residential mortgage and consumer TDRs on nonaccrual status at December 31, 2014.