Fair Value Measurements (Carrying Amounts and Estimated Fair Values for Certain Financial Instruments) (Detail) - USD ($) $ in Millions		Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Financial assets:
Cash and due from banks		$ 2,749	$ 2,681	$ 2,038	$ 2,514
Other short-term investments	[1]	3,556	1,825
Held-to-matury securities	[2]	21	18
Loans and leases held for sale	[3]	692	607
Commercial and industrial loans		51,862	44,340
Commercial mortgage loans		10,686	6,974
Commercial construction loans		5,231	4,657
Commercial leases		3,909	3,600
Residential mortgage loans		16,811	15,504
Home equity		6,435	6,402
Indirect secured consumer loans		10,031	8,976
Credit card		2,388	2,470
Other consumer loans and leases		2,489	2,342
Portfolio loans and leases, net		108,727	94,162
Financial liabilities:
Deposits		123,664	108,835
Federal funds purchased		2,630	1,925
Other short-term borrowings		1,329	573
Long-term debt	[1]	15,483	14,426
Net Carrying Amount
Financial assets:
Cash and due from banks		2,749	2,681
Other short-term investments		3,556	1,825
Other securities		581	552
Held-to-matury securities		21	18
Loans and leases held for sale		44	63
Commercial and industrial loans		51,345	43,825
Commercial mortgage loans		10,603	6,894
Commercial construction loans		5,197	4,625
Commercial leases		3,889	3,582
Residential mortgage loans		16,542	15,244
Home equity		6,396	6,366
Indirect secured consumer loans		9,983	8,934
Credit card		2,238	2,314
Other consumer loans and leases		2,456	2,309
Unallocated Allowance For Loan And Lease Losses		(112)	(110)
Portfolio loans and leases, net		108,537	93,983
Financial liabilities:
Deposits		123,664	108,835
Federal funds purchased		2,630	1,925
Other short-term borrowings		1,329	573
Long-term debt		15,483	14,426
Total Fair Value
Financial assets:
Cash and due from banks		2,749	2,681
Other short-term investments		3,556	1,825
Other securities		581	552
Held-to-matury securities		21	18
Loans and leases held for sale		44	63
Commercial and industrial loans		52,138	44,668
Commercial mortgage loans		10,587	6,851
Commercial construction loans		5,263	4,688
Commercial leases		3,559	3,180
Residential mortgage loans		17,219	15,688
Home equity		6,722	6,719
Indirect secured consumer loans		9,871	8,717
Credit card		2,668	2,759
Other consumer loans and leases		2,610	2,428
Unallocated Allowance For Loan And Lease Losses		0	0
Portfolio loans and leases, net		110,637	95,698
Financial liabilities:
Deposits		123,627	108,782
Federal funds purchased		2,630	1,925
Other short-term borrowings		1,329	573
Long-term debt		16,045	14,732
Fair Value, Inputs, Level 1
Financial assets:
Cash and due from banks		2,749	2,681
Other short-term investments		3,556	1,825
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
Indirect secured consumer 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		2,630	1,925
Other short-term borrowings		0	0
Long-term debt		15,229	14,287
Fair Value, Inputs, Level 2
Financial assets:
Cash and due from banks		0	0
Other short-term investments		0	0
Other securities		581	552
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
Indirect secured consumer 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		123,627	108,782
Federal funds purchased		0	0
Other short-term borrowings		1,329	573
Long-term debt		816	445
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		21	18
Loans and leases held for sale		44	63
Commercial and industrial loans		52,138	44,668
Commercial mortgage loans		10,587	6,851
Commercial construction loans		5,263	4,688
Commercial leases		3,559	3,180
Residential mortgage loans		17,219	15,688
Home equity		6,722	6,719
Indirect secured consumer loans		9,871	8,717
Credit card		2,668	2,759
Other consumer loans and leases		2,610	2,428
Unallocated Allowance For Loan And Lease Losses		0	0
Portfolio loans and leases, net		110,637	95,698
Financial liabilities:
Deposits		0	0
Federal funds purchased		0	0
Other short-term borrowings		0	0
Long-term debt		$ 0	$ 0

[1] Includes $ 39 and $ 40 of other short-term investments , $ 573 and $ 668 of portfolio loans and leases, $ (3) and $ (4) of ALLL, $ 3 and $ 5 of other assets, $ 1 and $ 1 of other liabilities, and $ 510 and $ 606 of long-term debt from consolidated VIEs that are included in their respe ctive captions above at March 31, 2019 and December 31, 2018 , respectively. For further information refer to Note 13 .

[2] Fair value of $ 21 and $ 18 at March 31, 2019 and December 31, 2018 , respectively.

[3] Includes $ 626 and $ 537 of residential mortgage loans held for sale measured at fair value and $ 22 and $ 7 of commercial loans held for sale measured at fair value at March 31, 2019 and December 31, 2018 , respectively.