Fair Value Measurements (Carrying Amounts and Estimated Fair Values for Certain Financial Instruments) (Detail) - USD ($) $ in Millions		Sep. 30, 2016		Dec. 31, 2015		Sep. 30, 2015	Dec. 31, 2014
Financial assets:
Cash and due from banks		$ 2,164	[1]	$ 2,540	[1]	$ 2,455	$ 3,091
Held-to-maturity securities, amortized cost	[2]	56		70
Other short-term investments		2,995		2,671
Loans held for sale	[3]	1,060		903
Portfolio loans and leases, net		91,879		91,310
Other securities, fair value	[4]	30,689		29,044
Held-to-maturity securities, fair value		56		70
Loans held for sale		954		519
Financial liabilities:
Deposits	[5]	101,271		103,205
Federal funds purchased		126		151
Other short-term borrowings		3,494		1,507
Long-term debt	[1],[6]	16,890		15,810
Residential Mortgage
Financial assets:
Portfolio loans and leases at fair value		149				$ 173
Carrying (Reported) Amount, Fair Value Disclosure
Financial assets:
Cash and due from banks		2,164		2,540
Held-to-maturity securities, amortized cost		56		70
Other short-term investments		2,995		2,671
Loans held for sale		106		384
Portfolio loans and leases, net		91,730		91,143
Unallocated Allowance For Loan And Lease Losses		(115)		(115)
Financial liabilities:
Deposits		101,271		103,205
Federal funds purchased		126		151
Other short-term borrowings		3,494		1,507
Long-term debt		16,890		15,810	[7]
Carrying (Reported) Amount, Fair Value Disclosure | FHLB and FRB restricted stock holdings
Financial assets:
Other securities		606		604
Carrying (Reported) Amount, Fair Value Disclosure | Commercial and Industrial Loans | Commercial
Financial assets:
Portfolio loans and leases, net		41,987		41,479
Carrying (Reported) Amount, Fair Value Disclosure | Commercial Mortgage Loans | Commercial
Financial assets:
Portfolio loans and leases, net		6,770		6,840
Carrying (Reported) Amount, Fair Value Disclosure | Commercial Construction Loans | Commercial
Financial assets:
Portfolio loans and leases, net		3,891		3,190
Carrying (Reported) Amount, Fair Value Disclosure | Commercial Leases | Commercial
Financial assets:
Portfolio loans and leases, net		3,981		3,807
Carrying (Reported) Amount, Fair Value Disclosure | Residential Mortgage
Financial assets:
Portfolio loans and leases, net		14,398		13,449
Carrying (Reported) Amount, Fair Value Disclosure | Home Equity
Financial assets:
Portfolio loans and leases, net		7,806		8,234
Carrying (Reported) Amount, Fair Value Disclosure | Automobile Loans
Financial assets:
Portfolio loans and leases, net		10,307		11,453
Carrying (Reported) Amount, Fair Value Disclosure | Credit Card
Financial assets:
Portfolio loans and leases, net		2,075		2,160
Carrying (Reported) Amount, Fair Value Disclosure | Other Consumer Loans and Leases
Financial assets:
Portfolio loans and leases, net		630		646
Total Fair Value
Financial assets:
Cash and due from banks, fair value		2,164		2,540
Held-to-maturity securities, fair value		56		70
Other short term investments, fair value		2,995		2,671
Portfolio loans and leases at fair value		94,365		92,282
Financial liabilities:
Deposits, fair value		101,309		103,219
Federal funds purchased, fair value		126		151
Other short-term borrowings, fair value		3,494		1,507
Long term debt, fair value		17,647		16,228	[7]
Total Fair Value | Non Fair Value Option HFS Loans
Financial assets:
Loans held for sale		106		384
Total Fair Value | FHLB and FRB restricted stock holdings
Financial assets:
Other securities, fair value		606		604
Total Fair Value | Commercial and Industrial Loans | Commercial
Financial assets:
Portfolio loans and leases at fair value		43,257		41,802
Total Fair Value | Commercial Mortgage Loans | Commercial
Financial assets:
Portfolio loans and leases at fair value		6,714		6,656
Total Fair Value | Commercial Construction Loans | Commercial
Financial assets:
Portfolio loans and leases at fair value		3,629		2,918
Total Fair Value | Commercial Leases | Commercial
Financial assets:
Portfolio loans and leases at fair value		3,718		3,533
Total Fair Value | Residential Mortgage
Financial assets:
Portfolio loans and leases at fair value		15,282		14,061
Total Fair Value | Home Equity
Financial assets:
Portfolio loans and leases at fair value		8,636		8,948
Total Fair Value | Automobile Loans
Financial assets:
Portfolio loans and leases at fair value		10,037		11,170
Total Fair Value | Credit Card
Financial assets:
Portfolio loans and leases at fair value		2,450		2,551
Total Fair Value | Other Consumer Loans and Leases
Financial assets:
Portfolio loans and leases at fair value		642		643
Total Fair Value | Fair Value, Inputs, Level 1
Financial assets:
Cash and due from banks, fair value		2,164		2,540
Other short term investments, fair value		2,995		2,671
Financial liabilities:
Federal funds purchased, fair value		126		151
Long term debt, fair value		16,927		15,603	[7]
Total Fair Value | Fair Value, Inputs, Level 2
Financial liabilities:
Deposits, fair value		101,309		103,219
Other short-term borrowings, fair value		3,494		1,507
Long term debt, fair value		720		625	[7]
Total Fair Value | Fair Value, Inputs, Level 2 | FHLB and FRB restricted stock holdings
Financial assets:
Other securities, fair value		606		604
Total Fair Value | Fair Value, Inputs, Level 3
Financial assets:
Held-to-maturity securities, fair value		56		70
Portfolio loans and leases at fair value		94,365		92,282
Total Fair Value | Fair Value, Inputs, Level 3 | Non Fair Value Option HFS Loans
Financial assets:
Loans held for sale		106		384
Total Fair Value | Fair Value, Inputs, Level 3 | Commercial and Industrial Loans | Commercial
Financial assets:
Portfolio loans and leases at fair value		43,257		41,802
Total Fair Value | Fair Value, Inputs, Level 3 | Commercial Mortgage Loans | Commercial
Financial assets:
Portfolio loans and leases at fair value		6,714		6,656
Total Fair Value | Fair Value, Inputs, Level 3 | Commercial Construction Loans | Commercial
Financial assets:
Portfolio loans and leases at fair value		3,629		2,918
Total Fair Value | Fair Value, Inputs, Level 3 | Commercial Leases | Commercial
Financial assets:
Portfolio loans and leases at fair value		3,718		3,533
Total Fair Value | Fair Value, Inputs, Level 3 | Residential Mortgage
Financial assets:
Portfolio loans and leases at fair value		15,282		14,061
Total Fair Value | Fair Value, Inputs, Level 3 | Home Equity
Financial assets:
Portfolio loans and leases at fair value		8,636		8,948
Total Fair Value | Fair Value, Inputs, Level 3 | Automobile Loans
Financial assets:
Portfolio loans and leases at fair value		10,037		11,170
Total Fair Value | Fair Value, Inputs, Level 3 | Credit Card
Financial assets:
Portfolio loans and leases at fair value		2,450		2,551
Total Fair Value | Fair Value, Inputs, Level 3 | Other Consumer Loans and Leases
Financial assets:
Portfolio loans and leases at fair value		$ 642		$ 643

[1] Includes $ 112 and $ 152 of cash and due from banks, $ 1,560 and $ 2,537 of portfolio loans and leases , $ (28) and $ (28) of ALLL, $ 11 and $ 14 of other assets, $ 3 and $ 3 of other liabilities , and $ 1,422 and $ 2,487 of long-term debt from consolidated VIEs that are included in their respective captions above at September 30, 2016 and December 31, 2015 , respectively. For further information refer to Note 10 .

[2] Fair value of $ 56 and $ 70 at September 30, 2016 and December 31, 2015 , respectively.

[3] Includes $ 954 and $ 519 of residential mortgage loans held for sale measured at fair value at September 30, 2016 and December 31, 2015 , respectively.

[4] Amortized cost of $ 29,486 and $ 28,678 at September 30, 2016 and Dec ember 31, 2015 , respectively.

[5] Includes $ 0 and $ 628 of deposits held for sale at September 30, 2016 and December 31, 2015 , respectively.

[6] Upon adoption of ASU 2015-03 on January 1, 2016, the December 31, 2015 Condensed Consolidated Balance Sheet was adjusted to reflect the reclassification of $34 of debt issuance costs from other assets to long-term debt. For further information refer to Note 3.

[7] (a) Upon adoption of ASU 2015-03 on January 1, 2016, the December 31, 2015 Condensed Consolidated Balance Sheet was adjusted to reflect the classification of $34 of debt issuance costs from other assets to long-term debt. For further information, refer to Note 3.