Fair Value Measurements (Carrying Amounts and Estimated Fair Values for Certain Financial Instruments) (Detail) - USD ($) $ in Millions		Sep. 30, 2017		Dec. 31, 2016		Sep. 30, 2016	Dec. 31, 2015	[1]
Financial assets:
Cash and due from banks		$ 2,205	[1]	$ 2,392	[1]	$ 2,164	$ 2,540
Held-to-maturity securities, amortized cost	[2]	25		26
Other short-term investments		3,298		2,754
Loans and leases held for sale	[3]	711		751
Portfolio loans and leases, net		90,678		90,845
Other securities, fair value	[4]	31,480		31,183
Held-to-maturity securities, fair value		25		26
Loans held for sale		651		686
Financial liabilities:
Deposits		101,452		103,821
Federal funds purchased		118		132
Other short-term borrowings		5,688		3,535
Long-term debt	[1]	14,039		14,388
Commercial
Financial assets:
Loans held for sale		5		0
Residential Mortgage
Financial assets:
Portfolio loans and leases at fair value		140				$ 149
Carrying (Reported) Amount, Fair Value Disclosure
Financial assets:
Cash and due from banks		2,205		2,392
Held-to-maturity securities, amortized cost		25		26
Other short-term investments		3,298		2,754
Loans and leases held for sale		55		65
Portfolio loans and leases, net		90,538		90,702
Unallocated Allowance For Loan And Lease Losses		(120)		(112)
Financial liabilities:
Deposits		101,452		103,821
Federal funds purchased		118		132
Other short-term borrowings		5,688		3,535
Long-term debt		14,039		14,388
Carrying (Reported) Amount, Fair Value Disclosure | FHLB, FRB and DTCC restricted stock holdings
Financial assets:
Other securities		611		607
Carrying (Reported) Amount, Fair Value Disclosure | Commercial and Industrial Loans | Commercial
Financial assets:
Portfolio loans and leases, net		40,341		40,958
Carrying (Reported) Amount, Fair Value Disclosure | Commercial Mortgage Loans | Commercial
Financial assets:
Portfolio loans and leases, net		6,791		6,817
Carrying (Reported) Amount, Fair Value Disclosure | Commercial Construction Loans | Commercial
Financial assets:
Portfolio loans and leases, net		4,628		3,887
Carrying (Reported) Amount, Fair Value Disclosure | Commercial Leases | Commercial
Financial assets:
Portfolio loans and leases, net		4,032		3,959
Carrying (Reported) Amount, Fair Value Disclosure | Residential Mortgage
Financial assets:
Portfolio loans and leases, net		15,358		14,812
Carrying (Reported) Amount, Fair Value Disclosure | Home Equity
Financial assets:
Portfolio loans and leases, net		7,096		7,637
Carrying (Reported) Amount, Fair Value Disclosure | Automobile Loans
Financial assets:
Portfolio loans and leases, net		9,197		9,941
Carrying (Reported) Amount, Fair Value Disclosure | Credit Card
Financial assets:
Portfolio loans and leases, net		2,061		2,135
Carrying (Reported) Amount, Fair Value Disclosure | Other Consumer Loans
Financial assets:
Portfolio loans and leases, net		1,154		668
Total Fair Value
Financial assets:
Cash and due from banks, fair value		2,205		2,392
Held-to-maturity securities, fair value		25		26
Other short term investments, fair value		3,298		2,754
Portfolio loans and leases at fair value		92,911		92,872
Financial liabilities:
Deposits, fair value		101,425		103,811
Federal funds purchased, fair value		118		132
Other short-term borrowings, fair value		5,688		3,535
Long term debt, fair value		14,778		14,833
Total Fair Value | Non Fair Value Option HFS Loans
Financial assets:
Loans held for sale		55		65
Total Fair Value | FHLB, FRB and DTCC restricted stock holdings
Financial assets:
Other securities, fair value		611		607
Total Fair Value | Commercial and Industrial Loans | Commercial
Financial assets:
Portfolio loans and leases at fair value		41,503		41,976
Total Fair Value | Commercial Mortgage Loans | Commercial
Financial assets:
Portfolio loans and leases at fair value		6,742		6,735
Total Fair Value | Commercial Construction Loans | Commercial
Financial assets:
Portfolio loans and leases at fair value		4,637		3,853
Total Fair Value | Commercial Leases | Commercial
Financial assets:
Portfolio loans and leases at fair value		3,698		3,651
Total Fair Value | Residential Mortgage
Financial assets:
Portfolio loans and leases at fair value		16,093		15,415
Total Fair Value | Home Equity
Financial assets:
Portfolio loans and leases at fair value		7,557		8,421
Total Fair Value | Automobile Loans
Financial assets:
Portfolio loans and leases at fair value		8,982		9,640
Total Fair Value | Credit Card
Financial assets:
Portfolio loans and leases at fair value		2,473		2,503
Total Fair Value | Other Consumer Loans
Financial assets:
Portfolio loans and leases at fair value		1,226		678
Total Fair Value | Fair Value, Inputs, Level 1
Financial assets:
Cash and due from banks, fair value		2,205		2,392
Other short term investments, fair value		3,298		2,754
Financial liabilities:
Federal funds purchased, fair value		118		132
Long term debt, fair value		14,244		14,288
Total Fair Value | Fair Value, Inputs, Level 2
Financial liabilities:
Deposits, fair value		101,425		103,811
Other short-term borrowings, fair value		5,688		3,535
Long term debt, fair value		534		545
Total Fair Value | Fair Value, Inputs, Level 2 | FHLB, FRB and DTCC restricted stock holdings
Financial assets:
Other securities, fair value		611		607
Total Fair Value | Fair Value, Inputs, Level 3
Financial assets:
Held-to-maturity securities, fair value		25		26
Portfolio loans and leases at fair value		92,911		92,872
Total Fair Value | Fair Value, Inputs, Level 3 | Non Fair Value Option HFS Loans
Financial assets:
Loans held for sale		55		65
Total Fair Value | Fair Value, Inputs, Level 3 | Commercial and Industrial Loans | Commercial
Financial assets:
Portfolio loans and leases at fair value		41,503		41,976
Total Fair Value | Fair Value, Inputs, Level 3 | Commercial Mortgage Loans | Commercial
Financial assets:
Portfolio loans and leases at fair value		6,742		6,735
Total Fair Value | Fair Value, Inputs, Level 3 | Commercial Construction Loans | Commercial
Financial assets:
Portfolio loans and leases at fair value		4,637		3,853
Total Fair Value | Fair Value, Inputs, Level 3 | Commercial Leases | Commercial
Financial assets:
Portfolio loans and leases at fair value		3,698		3,651
Total Fair Value | Fair Value, Inputs, Level 3 | Residential Mortgage
Financial assets:
Portfolio loans and leases at fair value		16,093		15,415
Total Fair Value | Fair Value, Inputs, Level 3 | Home Equity
Financial assets:
Portfolio loans and leases at fair value		7,557		8,421
Total Fair Value | Fair Value, Inputs, Level 3 | Automobile Loans
Financial assets:
Portfolio loans and leases at fair value		8,982		9,640
Total Fair Value | Fair Value, Inputs, Level 3 | Credit Card
Financial assets:
Portfolio loans and leases at fair value		2,473		2,503
Total Fair Value | Fair Value, Inputs, Level 3 | Other Consumer Loans
Financial assets:
Portfolio loans and leases at fair value		$ 1,226		$ 678

[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] Fair value of $ 25 and $ 26 at September 30, 2017 and December 31, 2016 , respectively.

[3] Includes $ 651 and $ 686 of residential mortgage loans held for sale measured at fair value and $ 5 and $ 0 of commercial loans held for sale measured at fair value at September 30, 2017 and December 31, 2016 , respectively.

[4] Amortized cost of $ 31,114 and $ 31,024 at September 30, 2017 and December 31, 2016 , respectively.