Fair Value Measurements (Carrying Amounts and Estimated Fair Values for Certain Financial Instruments) (Detail) - USD ($) $ in Millions		Sep. 30, 2018		Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Financial assets:
Cash and due from banks		$ 2,100		$ 2,514	$ 2,205	$ 2,392
Other short-term investments	[1]	1,429		2,753
Held-to-matury securities	[2]	18		24
Loans and leases held for sale		663	[3]	492
Commercial and industrial loans		42,631		41,170
Commercial mortgage loans		6,695		6,604
Commercial construction loans		4,892		4,553
Commercial leases		3,697		4,068
Residential mortgage loans		15,585		15,591
Home equity		6,485		7,014
Automobile loans		9,002		9,112
Credit card		2,325		2,299
Other consumer loans and leases		2,131		1,559
Portfolio loans and leases, net		92,352		90,774
Financial liabilities:
Deposits		104,342		103,162
Federal funds purchased		2,316		174
Other short-term borrowings		1,114		4,012
Long-term debt	[1]	14,460		14,904
Net Carrying Amount
Financial assets:
Cash and due from banks		2,100		2,514
Other short-term investments		1,429		2,753
Other securities		551		612
Held-to-matury securities		18		24
Loans and leases held for sale		94		93
Commercial and industrial loans		42,098		40,519
Commercial mortgage loans		6,622		6,539
Commercial construction loans		4,863		4,530
Commercial leases		3,676		4,054
Residential mortgage loans		15,330		15,365
Home equity		6,448		6,968
Automobile loans		8,963		9,074
Credit card		2,189		2,182
Other consumer loans and leases		2,100		1,526
Unallocated Allowance For Loan And Lease Losses		(109)		(120)
Portfolio loans and leases, net		92,180		90,637
Total Fair Value
Financial assets:
Cash and due from banks		2,100		2,514
Other short-term investments		1,429		2,753
Other securities		551		612
Held-to-matury securities		18		24
Loans and leases held for sale		94		93
Commercial and industrial loans		43,066		41,718
Commercial mortgage loans		6,556		6,490
Commercial construction loans		4,920		4,560
Commercial leases		3,266		3,705
Residential mortgage loans		15,544		15,996
Home equity		6,816		7,410
Automobile loans		8,687		8,832
Credit card		2,599		2,616
Other consumer loans and leases		2,205		1,621
Unallocated Allowance For Loan And Lease Losses		0		0
Portfolio loans and leases, net		93,659		92,948
Financial liabilities:
Deposits		104,279		103,123
Federal funds purchased		2,316		174
Other short-term borrowings		1,114		4,012
Long-term debt		14,632		15,574
Fair Value, Inputs, Level 1
Financial assets:
Cash and due from banks		2,100		2,514
Other short-term investments		1,429		2,753
Other securities		0		0
Held-to-matury securities		0		0
Loans and leases held for sale		0		0
Commercial and industrial loans		0		0
Commercial mortgage loans		0		0
Commercial construction loans		0		0
Commercial leases		0		0
Residential mortgage loans		0		0
Home equity		0		0
Automobile loans		0		0
Credit card		0		0
Other consumer loans and leases		0		0
Unallocated Allowance For Loan And Lease Losses		0		0
Portfolio loans and leases, net		0		0
Financial liabilities:
Deposits		0		0
Federal funds purchased		2,316		174
Other short-term borrowings		0		0
Long-term debt		14,200		15,045
Fair Value, Inputs, Level 2
Financial assets:
Cash and due from banks		0		0
Other short-term investments		0		0
Other securities		551		612
Held-to-matury securities		0		0
Loans and leases held for sale		0		0
Commercial and industrial loans		0		0
Commercial mortgage loans		0		0
Commercial construction loans		0		0
Commercial leases		0		0
Residential mortgage loans		0		0
Home equity		0		0
Automobile loans		0		0
Credit card		0		0
Other consumer loans and leases		0		0
Unallocated Allowance For Loan And Lease Losses		0		0
Portfolio loans and leases, net		0		0
Financial liabilities:
Deposits		104,279		103,123
Federal funds purchased		0		0
Other short-term borrowings		1,114		4,012
Long-term debt		432		529
Fair Value, Inputs, Level 3
Financial assets:
Cash and due from banks		0		0
Other short-term investments		0		0
Other securities		0		0
Held-to-matury securities		18		24
Loans and leases held for sale		94		93
Commercial and industrial loans		43,066		41,718
Commercial mortgage loans		6,556		6,490
Commercial construction loans		4,920		4,560
Commercial leases		3,266		3,705
Residential mortgage loans		15,544		15,996
Home equity		6,816		7,410
Automobile loans		8,687		8,832
Credit card		2,599		2,616
Other consumer loans and leases		2,205		1,621
Unallocated Allowance For Loan And Lease Losses		0		0
Portfolio loans and leases, net		93,659		92,948
Financial liabilities:
Deposits		0		0
Federal funds purchased		0		0
Other short-term borrowings		0		0
Long-term debt		$ 0		$ 0

[1] Includes $ 41 and $ 62 of other short-term investments , $ 793 and $ 1,297 of portfolio loans and leases, $ (4) and $ (6) of ALLL, $ 5 and $ 7 of other assets, $ 1 and $ 2 of other liabilities, and $ 710 and $ 1,190 of long-term debt from consolidated VIEs that are included in their respe ctive captions above at September 30, 2018 and December 31, 2017 , respectively. For further information refer to Note 10 .

[2] Fair value of $ 18 and $ 24 at September 30, 2018 and December 31, 2017 , respectively.

[3] Includes $ 563 and $ 399 of residential mortgage loans held for sale measured at fair value and $ 6 and $ 0 of commercial loans held for sale measured at fair value at September 30, 2018 and December 31, 2017 , respectively.