Fair Value Measurements (Carrying Amounts and Estimated Fair Values for Certain Financial Instruments) (Detail) - USD ($) $ in Millions		Mar. 31, 2017		Dec. 31, 2016		Mar. 31, 2016	Dec. 31, 2015
Financial assets:
Cash and due from banks		$ 2,205	[1]	$ 2,392	[1]	$ 2,298	$ 2,540
Held-to-maturity securities, amortized cost	[2]	26		26
Other short-term investments		1,644		2,754
Loans held for sale	[3]	616		751
Portfolio loans and leases, net		90,390		90,845
Other securities, fair value	[4]	31,531		31,183
Held-to-maturity securities, fair value		26		26
Loans held for sale		606		686
Financial liabilities:
Deposits		104,156		103,821
Federal funds purchased		155		132
Other short-term borrowings		2,015		3,535
Long-term debt	[1]	13,658		14,388
Residential Mortgage
Financial assets:
Portfolio loans and leases at fair value		141				$ 160
Carrying (Reported) Amount, Fair Value Disclosure
Financial assets:
Cash and due from banks		2,205		2,392
Held-to-maturity securities, amortized cost		26		26
Other short-term investments		1,644		2,754
Loans held for sale		10		65
Portfolio loans and leases, net		90,249		90,702
Unallocated Allowance For Loan And Lease Losses		(112)		(112)
Financial liabilities:
Deposits		104,156		103,821
Federal funds purchased		155		132
Other short-term borrowings		2,015		3,535
Long-term debt		13,658		14,388
Carrying (Reported) Amount, Fair Value Disclosure | FHLB and FRB restricted stock holdings
Financial assets:
Other securities		608		607
Carrying (Reported) Amount, Fair Value Disclosure | Commercial and Industrial Loans | Commercial
Financial assets:
Portfolio loans and leases, net		40,362		40,958
Carrying (Reported) Amount, Fair Value Disclosure | Commercial Mortgage Loans | Commercial
Financial assets:
Portfolio loans and leases, net		6,838		6,817
Carrying (Reported) Amount, Fair Value Disclosure | Commercial Construction Loans | Commercial
Financial assets:
Portfolio loans and leases, net		4,268		3,887
Carrying (Reported) Amount, Fair Value Disclosure | Commercial Leases | Commercial
Financial assets:
Portfolio loans and leases, net		4,079		3,959
Carrying (Reported) Amount, Fair Value Disclosure | Residential Mortgage
Financial assets:
Portfolio loans and leases, net		15,099		14,812
Carrying (Reported) Amount, Fair Value Disclosure | Home Equity
Financial assets:
Portfolio loans and leases, net		7,415		7,637
Carrying (Reported) Amount, Fair Value Disclosure | Automobile Loans
Financial assets:
Portfolio loans and leases, net		9,530		9,941
Carrying (Reported) Amount, Fair Value Disclosure | Credit Card
Financial assets:
Portfolio loans and leases, net		1,975		2,135
Carrying (Reported) Amount, Fair Value Disclosure | Other Consumer Loans and Leases
Financial assets:
Portfolio loans and leases, net		795		668
Total Fair Value
Financial assets:
Cash and due from banks, fair value		2,205		2,392
Held-to-maturity securities, fair value		26		26
Other short term investments, fair value		1,644		2,754
Portfolio loans and leases at fair value		92,317		92,872
Financial liabilities:
Deposits, fair value		104,148		103,811
Federal funds purchased, fair value		155		132
Other short-term borrowings, fair value		2,015		3,535
Long term debt, fair value		14,135		14,833
Total Fair Value | Non Fair Value Option HFS Loans
Financial assets:
Loans held for sale		10		65
Total Fair Value | FHLB and FRB restricted stock holdings
Financial assets:
Other securities, fair value		608		607
Total Fair Value | Commercial and Industrial Loans | Commercial
Financial assets:
Portfolio loans and leases at fair value		41,567		41,976
Total Fair Value | Commercial Mortgage Loans | Commercial
Financial assets:
Portfolio loans and leases at fair value		6,776		6,735
Total Fair Value | Commercial Construction Loans | Commercial
Financial assets:
Portfolio loans and leases at fair value		4,238		3,853
Total Fair Value | Commercial Leases | Commercial
Financial assets:
Portfolio loans and leases at fair value		3,700		3,651
Total Fair Value | Residential Mortgage
Financial assets:
Portfolio loans and leases at fair value		15,459		15,415
Total Fair Value | Home Equity
Financial assets:
Portfolio loans and leases at fair value		8,194		8,421
Total Fair Value | Automobile Loans
Financial assets:
Portfolio loans and leases at fair value		9,246		9,640
Total Fair Value | Credit Card
Financial assets:
Portfolio loans and leases at fair value		2,307		2,503
Total Fair Value | Other Consumer Loans and Leases
Financial assets:
Portfolio loans and leases at fair value		830		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		1,644		2,754
Financial liabilities:
Federal funds purchased, fair value		155		132
Long term debt, fair value		13,608		14,288
Total Fair Value | Fair Value, Inputs, Level 2
Financial liabilities:
Deposits, fair value		104,148		103,811
Other short-term borrowings, fair value		2,015		3,535
Long term debt, fair value		527		545
Total Fair Value | Fair Value, Inputs, Level 2 | FHLB and FRB restricted stock holdings
Financial assets:
Other securities, fair value		608		607
Total Fair Value | Fair Value, Inputs, Level 3
Financial assets:
Held-to-maturity securities, fair value		26		26
Portfolio loans and leases at fair value		92,317		92,872
Total Fair Value | Fair Value, Inputs, Level 3 | Non Fair Value Option HFS Loans
Financial assets:
Loans held for sale		10		65
Total Fair Value | Fair Value, Inputs, Level 3 | Commercial and Industrial Loans | Commercial
Financial assets:
Portfolio loans and leases at fair value		41,567		41,976
Total Fair Value | Fair Value, Inputs, Level 3 | Commercial Mortgage Loans | Commercial
Financial assets:
Portfolio loans and leases at fair value		6,776		6,735
Total Fair Value | Fair Value, Inputs, Level 3 | Commercial Construction Loans | Commercial
Financial assets:
Portfolio loans and leases at fair value		4,238		3,853
Total Fair Value | Fair Value, Inputs, Level 3 | Commercial Leases | Commercial
Financial assets:
Portfolio loans and leases at fair value		3,700		3,651
Total Fair Value | Fair Value, Inputs, Level 3 | Residential Mortgage
Financial assets:
Portfolio loans and leases at fair value		15,459		15,415
Total Fair Value | Fair Value, Inputs, Level 3 | Home Equity
Financial assets:
Portfolio loans and leases at fair value		8,194		8,421
Total Fair Value | Fair Value, Inputs, Level 3 | Automobile Loans
Financial assets:
Portfolio loans and leases at fair value		9,246		9,640
Total Fair Value | Fair Value, Inputs, Level 3 | Credit Card
Financial assets:
Portfolio loans and leases at fair value		2,307		2,503
Total Fair Value | Fair Value, Inputs, Level 3 | Other Consumer Loans and Leases
Financial assets:
Portfolio loans and leases at fair value		$ 830		$ 678

[1] Includes $ 85 and $ 85 of cash and due from banks, $ 1,015 and $ 1,216 of portfolio loans and leases , $ (25) and $ (26) of ALLL, $ 7 and $ 9 of other assets, $ 2 and $ 3 of other liabilities , and $ 883 and $ 1,094 of long-term debt from consolidated VIEs that are included in their respective captions above at March 31, 2017 and December 31, 2016 , respectively. For further information refer to Note 10 .

[2] Fair value of $ 26 and $ 26 at March 31, 2017 and December 31, 2016 , respectively.

[3] Includes $ 606 and $ 686 of residential mortgage loans held for sale measured at fair value at March 31, 2017 and December 31, 2016 , respectively.

[4] Amortized cost of $ 31,348 and $ 31,024 at March 31, 2017 and December 31, 2016 , respectively.