Fair Value Measurements (Carrying Amounts and Estimated Fair Values for Certain Financial Instruments) (Detail) - USD ($) $ in Millions		Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016	[1]
Financial assets:
Cash and due from banks		$ 2,038	$ 2,514	$ 2,205	$ 2,392
Held-to-maturity securities, amortized cost	[2]	23	24
Other short-term investments	[1]	1,747	2,753
Loans and leases held for sale	[3]	717	492
Portfolio loans and leases, net		90,832	90,774
Other securities, fair value	[4]	31,819	31,751
Held-to-maturity securities, fair value		23	24
Loans held for sale		650	399
Financial liabilities:
Deposits		105,461	103,162
Federal funds purchased		178	174
Other short-term borrowings		1,335	4,012
Long-term debt	[1]	14,800	14,904
Commercial
Financial assets:
Loans held for sale		16	0
Residential Mortgage
Financial assets:
Portfolio loans and leases at fair value		136		$ 141
Carrying (Reported) Amount, Fair Value Disclosure
Financial assets:
Cash and due from banks		2,038	2,514
Held-to-maturity securities, amortized cost		23	24
Other short-term investments		1,747	2,753
Loans and leases held for sale		51	93
Portfolio loans and leases, net		90,696	90,637
Unallocated Allowance For Loan And Lease Losses		(114)	(120)
Financial liabilities:
Deposits		105,461	103,162
Federal funds purchased		178	174
Other short-term borrowings		1,335	4,012
Long-term debt		14,800	14,904
Carrying (Reported) Amount, Fair Value Disclosure | FHLB, FRB and DTCC restricted stock holdings
Financial assets:
Other securities		612	612
Carrying (Reported) Amount, Fair Value Disclosure | Commercial and Industrial Loans | Commercial
Financial assets:
Portfolio loans and leases, net		41,023	40,519
Carrying (Reported) Amount, Fair Value Disclosure | Commercial Mortgage Loans | Commercial
Financial assets:
Portfolio loans and leases, net		6,446	6,539
Carrying (Reported) Amount, Fair Value Disclosure | Commercial Construction Loans | Commercial
Financial assets:
Portfolio loans and leases, net		4,743	4,530
Carrying (Reported) Amount, Fair Value Disclosure | Commercial Leases | Commercial
Financial assets:
Portfolio loans and leases, net		3,904	4,054
Carrying (Reported) Amount, Fair Value Disclosure | Residential Mortgage
Financial assets:
Portfolio loans and leases, net		15,338	15,365
Carrying (Reported) Amount, Fair Value Disclosure | Home Equity
Financial assets:
Portfolio loans and leases, net		6,713	6,968
Carrying (Reported) Amount, Fair Value Disclosure | Automobile Loans
Financial assets:
Portfolio loans and leases, net		8,979	9,074
Carrying (Reported) Amount, Fair Value Disclosure | Credit Card
Financial assets:
Portfolio loans and leases, net		2,072	2,182
Carrying (Reported) Amount, Fair Value Disclosure | Other Consumer Loans
Financial assets:
Portfolio loans and leases, net		1,592	1,526
Total Fair Value
Financial assets:
Cash and due from banks, fair value		2,038	2,514
Held-to-maturity securities, fair value		23	24
Other short term investments, fair value		1,747	2,753
Portfolio loans and leases at fair value		92,469	92,948
Financial liabilities:
Deposits, fair value		105,407	103,123
Federal funds purchased, fair value		178	174
Other short-term borrowings, fair value		1,335	4,012
Long term debt, fair value		15,216	15,574
Total Fair Value | Non Fair Value Option HFS Loans
Financial assets:
Loans held for sale		51	93
Total Fair Value | FHLB, FRB and DTCC restricted stock holdings
Financial assets:
Other securities, fair value		612	612
Total Fair Value | Commercial and Industrial Loans | Commercial
Financial assets:
Portfolio loans and leases at fair value		42,143	41,718
Total Fair Value | Commercial Mortgage Loans | Commercial
Financial assets:
Portfolio loans and leases at fair value		6,395	6,490
Total Fair Value | Commercial Construction Loans | Commercial
Financial assets:
Portfolio loans and leases at fair value		4,775	4,560
Total Fair Value | Commercial Leases | Commercial
Financial assets:
Portfolio loans and leases at fair value		3,520	3,705
Total Fair Value | Residential Mortgage
Financial assets:
Portfolio loans and leases at fair value		15,716	15,996
Total Fair Value | Home Equity
Financial assets:
Portfolio loans and leases at fair value		7,103	7,410
Total Fair Value | Automobile Loans
Financial assets:
Portfolio loans and leases at fair value		8,708	8,832
Total Fair Value | Credit Card
Financial assets:
Portfolio loans and leases at fair value		2,440	2,616
Total Fair Value | Other Consumer Loans
Financial assets:
Portfolio loans and leases at fair value		1,669	1,621
Total Fair Value | Fair Value, Inputs, Level 1
Financial assets:
Cash and due from banks, fair value		2,038	2,514
Other short term investments, fair value		1,747	2,753
Financial liabilities:
Federal funds purchased, fair value		178	174
Long term debt, fair value		14,752	15,045
Total Fair Value | Fair Value, Inputs, Level 2
Financial liabilities:
Deposits, fair value		105,407	103,123
Other short-term borrowings, fair value		1,335	4,012
Long term debt, fair value		464	529
Total Fair Value | Fair Value, Inputs, Level 2 | FHLB, FRB and DTCC restricted stock holdings
Financial assets:
Other securities, fair value		612	612
Total Fair Value | Fair Value, Inputs, Level 3
Financial assets:
Held-to-maturity securities, fair value		23	24
Portfolio loans and leases at fair value		92,469	92,948
Total Fair Value | Fair Value, Inputs, Level 3 | Non Fair Value Option HFS Loans
Financial assets:
Loans held for sale		51	93
Total Fair Value | Fair Value, Inputs, Level 3 | Commercial and Industrial Loans | Commercial
Financial assets:
Portfolio loans and leases at fair value		42,143	41,718
Total Fair Value | Fair Value, Inputs, Level 3 | Commercial Mortgage Loans | Commercial
Financial assets:
Portfolio loans and leases at fair value		6,395	6,490
Total Fair Value | Fair Value, Inputs, Level 3 | Commercial Construction Loans | Commercial
Financial assets:
Portfolio loans and leases at fair value		4,775	4,560
Total Fair Value | Fair Value, Inputs, Level 3 | Commercial Leases | Commercial
Financial assets:
Portfolio loans and leases at fair value		3,520	3,705
Total Fair Value | Fair Value, Inputs, Level 3 | Residential Mortgage
Financial assets:
Portfolio loans and leases at fair value		15,716	15,996
Total Fair Value | Fair Value, Inputs, Level 3 | Home Equity
Financial assets:
Portfolio loans and leases at fair value		7,103	7,410
Total Fair Value | Fair Value, Inputs, Level 3 | Automobile Loans
Financial assets:
Portfolio loans and leases at fair value		8,708	8,832
Total Fair Value | Fair Value, Inputs, Level 3 | Credit Card
Financial assets:
Portfolio loans and leases at fair value		2,440	2,616
Total Fair Value | Fair Value, Inputs, Level 3 | Other Consumer Loans
Financial assets:
Portfolio loans and leases at fair value		$ 1,669	$ 1,621

[1] Includes $ 66 and $ 62 of other short-term investments , $ 1,135 and $ 1,297 of portfolio loans and leases, $ (6) and $ (6) of ALLL, $ 6 and $ 7 of other assets, $ 2 and $ 2 of other liabilities, and $ 1,031 and $ 1,190 of long-term debt from consolidated VIEs that are included in their respe ctive captions above at March 31, 2018 and December 31, 2017 , respectively. For further information refer to Note 9 .

[2] Fair value of $ 23 and $ 24 at March 31, 2018 and December 31, 2017 , respectively.

[3] Includes $ 650 and $ 399 of residential mortgage loans held for sale measured at fair value and $ 16 and $ 0 of commercial loans held for sale measured at fair value at March 31, 2018 and December 31, 2017 , respectively.

[4] Amortized cost of $ 32,230 and $ 31,577 at March 31, 2018 and December 31, 2017 , respectively.