Credit Quality (Summary of the ALLL and Related Loans and Leases Classified by Portfolio Segment) (Parenthetical) (Detail) $ in Millions	3 Months Ended				9 Months Ended				12 Months Ended
	Sep. 30, 2016 USD ($)		Sep. 30, 2015 USD ($)		Sep. 30, 2016 USD ($)		Sep. 30, 2015 USD ($)		Dec. 31, 2015 USD ($)		Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)	Dec. 31, 2014 USD ($)
Financing Receivable, Allowance for Credit Losses
Allowance for loan and lease losses	$ 1,272	[1],[2]	$ 1,261		$ 1,272	[1],[2]	$ 1,261		$ 1,272	[1],[3]	$ 1,299	$ 1,293	$ 1,322
Portfolio loans and leases	$ 93,002	[4],[5]			$ 93,002	[4],[5]			92,415	[6],[7]
Number of contracts	2,687	[8],[9]	3,551	[10],[11]	8,366	[8],[9]	11,227	[10],[11]
Recorded investment	$ 1,914	[12]			$ 1,914	[12]			1,842	[13]
Variable Interest Entity, Primary Beneficiary
Financing Receivable, Allowance for Credit Losses
Allowance for loan and lease losses	28				28				28
Commercial | Variable Interest Entity, Primary Beneficiary
Financing Receivable, Allowance for Credit Losses
Allowance for loan and lease losses	18				$ 18				$ 15
Number of contracts					5				5
Recorded investment	27				$ 27				$ 27
Leveraged Leases
Financing Receivable, Allowance for Credit Losses
Allowance for loan and lease losses	2				2				5
Portfolio loans and leases	725				725				801
Residential Mortgage Loans
Financing Receivable, Allowance for Credit Losses
Portfolio loans and leases at fair value	$ 149				$ 149				$ 167

[1] Includes $ 112 and $ 152 of cash and due from banks, $ 1,560 and $ 2,537 of portfolio loans and leases , $ (28) and $ (28) of ALLL, $ 11 and $ 14 of other assets, $ 3 and $ 3 of other liabilities , and $ 1,422 and $ 2,487 of long-term debt from consolidated VIEs that are included in their respective captions above at September 30, 2016 and December 31, 2015 , respectively. For further information refer to Note 10 .

[2] Includes $ 2 related to leveraged leases at September 30, 2016 .

[3] Includes $ 5 related to leveraged leases at December 31, 2015 .

[4] Excludes $ 149 of residential mortgage loans measured at fair value at September 30, 2016 .

[5] Excludes $ 149 of residential mortgage loans measured at fair value, and includes $ 72 5 of leveraged leases, net of unearned income at September 30, 2016 .

[6] Excludes $ 167 of residential mortgage loans measured at fair value at December 31, 2015 .

[7] Excludes $ 167 of residential mortgage loans measured at fair value, and includes $ 801 of leveraged leases, net of unearned income at December 31, 2015 .

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

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

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

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

[12] Includes $ 408 , $ 638 and $ 334 , respectively, of commercial, residential mortgage and consumer portfolio TDRs on accrual status and $ 194 , $ 13 an d $ 50 , respectively , of commercial , residential mortgage and consumer portfolio TDRs on nonaccrual status at September 30, 2016 .

[13] Includes $ 491 , $ 607 and $ 327 , respectively, of commercial, residential mortgage and consumer portfolio TDR s on accrual status and $ 203 , $ 23 and $ 52 , respectively , of commercial, residential mortgage and consumer portfolio TDRs on nonaccrual status at December 31, 2015 .