Fair Value Measurements (Carrying Amounts and Estimated Fair Values for Certain Financial Instruments) (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Financial assets:
Cash and due from banks	$ 3,278	$ 2,681	$ 2,514	$ 2,392
Other short-term investments	1,950	1,825
Held-to-maturity securities	17	18
Loans and leases held for sale	1,400	607
Commercial and industrial loans	50,542	44,340
Commercial mortgage loans	10,963	6,974
Commercial construction loans	5,090	4,657
Commercial leases	3,363	3,600
Residential mortgage loans	16,724	15,504
Home equity	6,083	6,402
Indirect secured consumer loans	11,538	8,976
Credit card	2,532	2,470
Other consumer loans	2,723	2,342
Portfolio loans and leases, net	108,356	94,162
Financial liabilities:
Deposits	127,062	108,835
Federal funds purchased	260	1,925
Other short-term borrowings	1,011	573
Long-term debt	14,970	14,426
Fair Value, Inputs, Level 1
Financial assets:
Cash and due from banks	3,278	2,681
Other short-term investments	1,950	1,825
Other securities	0	0
Held-to-maturity 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	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	260	1,925
Other short-term borrowings	0	0
Long-term debt	15,244	14,287
Fair Value, Inputs, Level 2
Financial assets:
Cash and due from banks	0	0
Other short-term investments	0	0
Other securities	556	552
Held-to-maturity 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	0	0
Unallocated Allowance for Loan and Lease Losses	0	0
Portfolio loans and leases, net	0	0
Financial liabilities:
Deposits	127,059	108,782
Federal funds purchased	0	0
Other short-term borrowings	1,011	573
Long-term debt	700	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-maturity securities	17	18
Loans and leases held for sale	136	63
Commercial and industrial loans	51,128	44,668
Commercial mortgage loans	10,823	6,851
Commercial construction loans	5,249	4,688
Commercial leases	3,133	3,180
Residential mortgage loans	17,509	15,688
Home equity	6,315	6,719
Indirect secured consumer loans	11,331	8,717
Credit card	2,774	2,759
Other consumer loans	2,866	2,428
Unallocated Allowance for Loan and Lease Losses	0	0
Portfolio loans and leases, net	111,128	95,698
Financial liabilities:
Deposits	0	0
Federal funds purchased	0	0
Other short-term borrowings	0	0
Long-term debt	0	0
Net Carrying Amount
Financial assets:
Cash and due from banks	3,278	2,681
Other short-term investments	1,950	1,825
Other securities	556	552
Held-to-maturity securities	17	18
Loans and leases held for sale	136	63
Commercial and industrial loans	49,981	43,825
Commercial mortgage loans	10,876	6,894
Commercial construction loans	5,045	4,625
Commercial leases	3,346	3,582
Residential mortgage loans	16,468	15,244
Home equity	6,046	6,366
Indirect secured consumer loans	11,485	8,934
Credit card	2,364	2,314
Other consumer loans	2,683	2,309
Unallocated Allowance for Loan and Lease Losses	(121)	(110)
Portfolio loans and leases, net	108,173	93,983
Financial liabilities:
Deposits	127,062	108,835
Federal funds purchased	260	1,925
Other short-term borrowings	1,011	573
Long-term debt	14,970	14,426
Total Fair Value
Financial assets:
Cash and due from banks	3,278	2,681
Other short-term investments	1,950	1,825
Other securities	556	552
Held-to-maturity securities	17	18
Loans and leases held for sale	136	63
Commercial and industrial loans	51,128	44,668
Commercial mortgage loans	10,823	6,851
Commercial construction loans	5,249	4,688
Commercial leases	3,133	3,180
Residential mortgage loans	17,509	15,688
Home equity	6,315	6,719
Indirect secured consumer loans	11,331	8,717
Credit card	2,774	2,759
Other consumer loans	2,866	2,428
Unallocated Allowance for Loan and Lease Losses	0	0
Portfolio loans and leases, net	111,128	95,698
Financial liabilities:
Deposits	127,059	108,782
Federal funds purchased	260	1,925
Other short-term borrowings	1,011	573
Long-term debt	$ 15,944	$ 14,732

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Loans and leases receivable gross consumer home equity.

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Loans and leases receivable gross consumer revolving credit card.

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Loans leases receivable consumer installments.

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For banks and other depository institutions: Includes cash on hand (currency and coin), cash items in process of collection, noninterest bearing deposits due from other financial institutions (including corporate credit unions), and noninterest bearing balances with the Federal Reserve Banks, Federal Home Loan Banks and central banks.

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Amount of investment in debt security measured at amortized cost (held-to-maturity).

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