Fair Value Measurements (Carrying Amounts and Estimated Fair Values for Certain Financial Instruments) (Detail) - USD ($) $ in Millions		Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015	Dec. 31, 2014
Financial assets:
Cash and due from banks		$ 2,514	[1]	$ 2,392	[1]	$ 2,540	$ 3,091
Held-to-maturity securities, amortized cost	[2]	24		26
Other short-term investments	[1]	2,753		2,754
Loans held for sale	[3]	492		751
Portfolio loans and leases, net		90,774		90,845
Other securities, fair value	[4]	31,820		31,183
Held-to-maturity securities, fair value		24		26
Loans held for sale		399		686
Portfolio loans and leases at fair value		137		143
Financial liabilities:
Deposits		103,162		103,821
Federal funds purchased		174		132
Other short-term borrowings		4,012		3,535
Long-term debt	[1]	14,904		14,388
Residential Mortgage
Financial assets:
Portfolio loans and leases at fair value		137		143
Carrying (Reported) Amount, Fair Value Disclosure
Financial assets:
Cash and due from banks		2,514		2,392
Held-to-maturity securities, amortized cost		24		26
Other short-term investments		2,753		2,754
Loans held for sale		93		65
Portfolio loans and leases, net		90,637		90,702
Unallocated Allowance for Loan and Lease Losses		(120)		(112)
Financial liabilities:
Deposits		103,162		103,821
Federal funds purchased		174		132
Other short-term borrowings		4,012		3,535
Long-term debt		14,904		14,388
Carrying (Reported) Amount, Fair Value Disclosure | FHLB and FRB restricted stock holdings
Financial assets:
Other securities		612		607
Carrying (Reported) Amount, Fair Value Disclosure | Commercial and Industrial Loans | Commercial
Financial assets:
Portfolio loans and leases, net		40,519		40,958
Carrying (Reported) Amount, Fair Value Disclosure | Commercial Mortgage Loans | Commercial
Financial assets:
Portfolio loans and leases, net		6,539		6,817
Carrying (Reported) Amount, Fair Value Disclosure | Commercial Construction Loans | Commercial
Financial assets:
Portfolio loans and leases, net		4,530		3,887
Carrying (Reported) Amount, Fair Value Disclosure | Commercial Leases | Commercial
Financial assets:
Portfolio loans and leases, net		4,054		3,959
Carrying (Reported) Amount, Fair Value Disclosure | Residential Mortgage
Financial assets:
Portfolio loans and leases, net		15,365		14,812
Carrying (Reported) Amount, Fair Value Disclosure | Home Equity
Financial assets:
Portfolio loans and leases, net		6,968		7,637
Carrying (Reported) Amount, Fair Value Disclosure | Automobile Loans
Financial assets:
Portfolio loans and leases, net		9,074		9,941
Carrying (Reported) Amount, Fair Value Disclosure | Credit Card
Financial assets:
Portfolio loans and leases, net		2,182		2,135
Carrying (Reported) Amount, Fair Value Disclosure | Other Consumer Loans and Leases
Financial assets:
Portfolio loans and leases, net		1,526		668
Total Fair Value
Financial assets:
Cash and due from banks, fair value		2,514		2,392
Held-to-maturity securities, fair value		24		26
Other short term investments, fair value		2,753		2,754
Portfolio loans and leases at fair value		92,948		92,872
Financial liabilities:
Deposits, fair value		103,123		103,811
Federal funds purchased, fair value		174		132
Other short-term borrowings, fair value		4,012		3,535
Long term debt, fair value		15,574		14,833
Total Fair Value | Non Fair Value Option HFS Loans
Financial assets:
Loans held for sale		93		65
Total Fair Value | FHLB and FRB restricted stock holdings
Financial assets:
Other securities, fair value		612		607
Total Fair Value | Commercial and Industrial Loans | Commercial
Financial assets:
Portfolio loans and leases at fair value		41,718		41,976
Total Fair Value | Commercial Mortgage Loans | Commercial
Financial assets:
Portfolio loans and leases at fair value		6,490		6,735
Total Fair Value | Commercial Construction Loans | Commercial
Financial assets:
Portfolio loans and leases at fair value		4,560		3,853
Total Fair Value | Commercial Leases | Commercial
Financial assets:
Portfolio loans and leases at fair value		3,705		3,651
Total Fair Value | Residential Mortgage
Financial assets:
Portfolio loans and leases at fair value		15,996		15,415
Total Fair Value | Home Equity
Financial assets:
Portfolio loans and leases at fair value		7,410		8,421
Total Fair Value | Automobile Loans
Financial assets:
Portfolio loans and leases at fair value		8,832		9,640
Total Fair Value | Credit Card
Financial assets:
Portfolio loans and leases at fair value		2,616		2,503
Total Fair Value | Other Consumer Loans and Leases
Financial assets:
Portfolio loans and leases at fair value		1,621		678
Total Fair Value | Fair Value, Inputs, Level 1
Financial assets:
Cash and due from banks, fair value		2,514		2,392
Other short term investments, fair value		2,753		2,754
Financial liabilities:
Federal funds purchased, fair value		174		132
Long term debt, fair value		15,045		14,288
Total Fair Value | Fair Value, Inputs, Level 2
Financial liabilities:
Deposits, fair value		103,123		103,811
Other short-term borrowings, fair value		4,012		3,535
Long term debt, fair value		529		545
Total Fair Value | Fair Value, Inputs, Level 2 | FHLB and FRB restricted stock holdings
Financial assets:
Other securities, fair value		612		607
Total Fair Value | Fair Value, Inputs, Level 3
Financial assets:
Held-to-maturity securities, fair value		24		26
Portfolio loans and leases at fair value		92,948		92,872
Total Fair Value | Fair Value, Inputs, Level 3 | Non Fair Value Option HFS Loans
Financial assets:
Loans held for sale		93		65
Total Fair Value | Fair Value, Inputs, Level 3 | Commercial and Industrial Loans | Commercial
Financial assets:
Portfolio loans and leases at fair value		41,718		41,976
Total Fair Value | Fair Value, Inputs, Level 3 | Commercial Mortgage Loans | Commercial
Financial assets:
Portfolio loans and leases at fair value		6,490		6,735
Total Fair Value | Fair Value, Inputs, Level 3 | Commercial Construction Loans | Commercial
Financial assets:
Portfolio loans and leases at fair value		4,560		3,853
Total Fair Value | Fair Value, Inputs, Level 3 | Commercial Leases | Commercial
Financial assets:
Portfolio loans and leases at fair value		3,705		3,651
Total Fair Value | Fair Value, Inputs, Level 3 | Residential Mortgage
Financial assets:
Portfolio loans and leases at fair value		15,996		15,415
Total Fair Value | Fair Value, Inputs, Level 3 | Home Equity
Financial assets:
Portfolio loans and leases at fair value		7,410		8,421
Total Fair Value | Fair Value, Inputs, Level 3 | Automobile Loans
Financial assets:
Portfolio loans and leases at fair value		8,832		9,640
Total Fair Value | Fair Value, Inputs, Level 3 | Credit Card
Financial assets:
Portfolio loans and leases at fair value		2,616		2,503
Total Fair Value | Fair Value, Inputs, Level 3 | Other Consumer Loans and Leases
Financial assets:
Portfolio loans and leases at fair value		$ 1,621		$ 678

[1] Includes $ 0 and $ 85 of cash and due from banks, $ 62 and $ 0 of other short-term investments, $ 1,297 and $ 1,216 of portfolio loans and leases, $ (6) and $ (26) of ALLL, $ 7 and $ 9 of other assets, $ 2 and $ 3 of other liabilities and $ 1,190 and $ 1,094 of long-term debt from consolidated VIEs that are included in their respective captions above at December 31, 2017 and 2016 , respectively. For further information, refer to Note 11 .

[2] Fair value of $ 24 and $ 26 at December 31, 2017 and 2016 , respectively.

[3] Includes $ 399 and $ 686 of residential mortgage loans held for sale measured at fair value at December 31, 2017 and 2016 , respectively.

[4] Amortized cost of $ 31,644 and $ 31,024 at December 31, 2017 and 2016 , respectively.