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, 2017 USD ($)		Sep. 30, 2016 USD ($)		Sep. 30, 2017 USD ($)		Sep. 30, 2016 USD ($)		Dec. 31, 2016 USD ($)		Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Financing Receivable, Allowance for Credit Losses
Allowance for loan and lease losses	$ 1,205	[1],[2]	$ 1,272		$ 1,205	[1],[2]	$ 1,272		$ 1,253	[1],[3]	$ 1,226	$ 1,226	$ 1,299	$ 1,299	$ 1,272
Portfolio loans and leases	$ 91,743	[4],[5]			$ 91,743	[4],[5]			91,955	[6],[7]
Number of contracts	2,353	[8],[9]	2,687	[10],[11]	6,842	[12],[13]	8,366	[14],[15]
Recorded investment	$ 1,587	[16]			$ 1,587	[16]			1,901	[17]
Variable Interest Entity, Primary Beneficiary
Financing Receivable, Allowance for Credit Losses
Allowance for loan and lease losses	8				8				26
Commercial | Variable Interest Entity, Primary Beneficiary
Financing Receivable, Allowance for Credit Losses
Allowance for loan and lease losses									$ 18
Number of contracts									5
Recorded investment									$ 26
Leveraged Leases
Financing Receivable, Allowance for Credit Losses
Allowance for loan and lease losses	1				1				2
Portfolio loans and leases	709				709				701
Residential Mortgage Loans
Financing Receivable, Allowance for Credit Losses
Portfolio loans and leases at fair value	$ 140				$ 140				$ 143

[1] Includes $ 116 and $ 85 of cash and due from banks, $ 1,532 and $ 1,216 of portfolio loans and leases , $ (8) and $ (26) of ALLL, $ 9 and $ 9 of other assets, $ 3 and $ 3 of other liabilities , and $ 1,491 and $ 1,094 of long-term debt from consolidated VIEs that are included in their respective captions above at September 30, 2017 and December 31, 2016 , respectively. For further information refer to Note 11 .

[2] Includes $ 1 related to leveraged leases at September 30, 2017 .

[3] Includes $ 2 related to leveraged leases at December 31, 2016 .

[4] Excludes $ 140 of residential mortgage loans measured at fair value and includes $ 7 09 of leveraged leases, net of unearned income at September 30, 2017 .

[5] Excludes $ 140 of residential mortgage loans measured at fair value at September 30, 2017 .

[6] Excludes $ 143 of residential mortgage loans measured at fair value at December 31, 2016 .

[7] Excludes $ 143 of residential mortga ge loans measured at fair value and includes $ 701 of leveraged leases, net of unearned income at December 31, 2016 .

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

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

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

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

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

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

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

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

[16] Includes $ 232 , $ 646 and $ 283 , respectively, of commercial, residential mortgage and consumer portfolio TDRs on accrual status and $ 214 , $ 12 an d $ 46 , respectively, of commercial, residential mortgage a nd consumer portfolio TDRs on nonaccrual status at September 30, 2017 .

[17] Includes $ 322 , $ 635 and $ 323 , respectively, of commercial, residential mortgage and consumer portfolio TDR s on accrual status and $ 192 , $ 17 and $ 48 , respectively , of commercial, residential mortgage and consumer portfolio TDRs on nonaccrual status at December 31, 2016 .