Fair Value Measurements (Carrying Amounts and Estimated Fair Values for Certain Financial Instruments) (Detail) - USD ($) $ in Millions		Jun. 30, 2016		Dec. 31, 2015		Jun. 30, 2015	Dec. 31, 2014
Financial assets:
Cash and due from banks		$ 2,359	[1]	$ 2,540	[1]	$ 2,785	$ 3,091
Held-to-maturity securities, amortized cost	[2]	62		70
Other short-term investments		1,818		2,671
Loans held for sale	[3]	877		903
Portfolio loans and leases, net		92,610		91,310
Other securities, fair value	[4]	31,455		29,044
Held-to-maturity securities, fair value		62		70
Loans held for sale		852		519
Financial liabilities:
Deposits	[5]	101,871		103,205
Federal funds purchased		108		151
Other short-term borrowings		3,979		1,507
Long-term debt	[1],[6]	16,231		15,810
Residential Mortgage
Financial assets:
Portfolio loans and leases at fair value		154				$ 178
Carrying (Reported) Amount, Fair Value Disclosure
Financial assets:
Cash and due from banks		2,359		2,540
Held-to-maturity securities, amortized cost		62		70
Other short-term investments		1,818		2,671
Loans held for sale		25		384
Unallocated Allowance For Loan And Lease Losses		(117)		(115)
Portfolio loans and leases at fair value		92,456		91,143
Financial liabilities:
Deposits		101,871		103,205
Federal funds purchased		108		151
Other short-term borrowings		3,979		1,507
Long-term debt		16,231		15,810
Carrying (Reported) Amount, Fair Value Disclosure | FHLB and FRB restricted stock holdings
Financial assets:
Other securities		605		604
Carrying (Reported) Amount, Fair Value Disclosure | Commercial and Industrial Loans | Commercial
Financial assets:
Portfolio loans and leases, net		42,800		41,479
Carrying (Reported) Amount, Fair Value Disclosure | Commercial Mortgage Loans | Commercial
Financial assets:
Portfolio loans and leases, net		6,789		6,840
Carrying (Reported) Amount, Fair Value Disclosure | Commercial Construction Loans | Commercial
Financial assets:
Portfolio loans and leases, net		3,692		3,190
Carrying (Reported) Amount, Fair Value Disclosure | Commercial Leases | Commercial
Financial assets:
Portfolio loans and leases, net		3,963		3,807
Carrying (Reported) Amount, Fair Value Disclosure | Residential Mortgage
Financial assets:
Portfolio loans and leases, net		14,055		13,449
Carrying (Reported) Amount, Fair Value Disclosure | Home Equity
Financial assets:
Portfolio loans and leases, net		7,927		8,234
Carrying (Reported) Amount, Fair Value Disclosure | Automobile Loan [Member]
Financial assets:
Portfolio loans and leases, net		10,633		11,453
Carrying (Reported) Amount, Fair Value Disclosure | Credit Card Receivables [Member]
Financial assets:
Portfolio loans and leases, net		2,077		2,160
Carrying (Reported) Amount, Fair Value Disclosure | Other Consumer Loans and Leases
Financial assets:
Portfolio loans and leases, net		637		646
Total Fair Value
Financial assets:
Cash and due from banks, fair value		2,359		2,540
Held-to-maturity securities, fair value		62		70
Other short term investments, fair value		1,818		2,671
Portfolio loans and leases at fair value		95,053		92,282
Financial liabilities:
Deposits, fair value		101,940		103,219
Federal funds purchased, fair value		108		151
Other short-term borrowings, fair value		3,979		1,507
Long term debt, fair value		17,017		16,228
Total Fair Value | Non Fair Value Option Held For Sale Loans [Member]
Financial assets:
Loans held for sale		25		384
Total Fair Value | FHLB and FRB restricted stock holdings
Financial assets:
Other securities, fair value		605		604
Total Fair Value | Commercial and Industrial Loans | Commercial
Financial assets:
Portfolio loans and leases at fair value		43,981		41,802
Total Fair Value | Commercial Mortgage Loans | Commercial
Financial assets:
Portfolio loans and leases, net		6,692		6,656
Total Fair Value | Commercial Construction Loans | Commercial
Financial assets:
Portfolio loans and leases, net		3,436		2,918
Total Fair Value | Commercial Leases | Commercial
Financial assets:
Portfolio loans and leases, net		3,739		3,533
Total Fair Value | Residential Mortgage
Financial assets:
Portfolio loans and leases at fair value		14,937		14,061
Total Fair Value | Home Equity
Financial assets:
Portfolio loans and leases at fair value		8,790		8,948
Total Fair Value | Automobile Loan [Member]
Financial assets:
Portfolio loans and leases at fair value		10,392		11,170
Total Fair Value | Credit Card Receivables [Member]
Financial assets:
Portfolio loans and leases at fair value		2,437		2,551
Total Fair Value | Other Consumer Loans and Leases
Financial assets:
Portfolio loans and leases, net		649		643
Total Fair Value | Fair Value, Inputs, Level 1
Financial assets:
Cash and due from banks, fair value		2,359		2,540
Other short term investments, fair value		1,818		2,671
Financial liabilities:
Federal funds purchased, fair value		108		151
Long term debt, fair value		16,283		15,603
Total Fair Value | Fair Value, Inputs, Level 2
Financial liabilities:
Deposits, fair value		101,940		103,219
Other short-term borrowings, fair value		3,979		1,507
Long term debt, fair value		734		625
Total Fair Value | Fair Value, Inputs, Level 2 | FHLB and FRB restricted stock holdings
Financial assets:
Other securities, fair value		605		604
Total Fair Value | Fair Value, Inputs, Level 3
Financial assets:
Held-to-maturity securities, fair value		62		70
Portfolio loans and leases at fair value		95,053		92,282
Total Fair Value | Fair Value, Inputs, Level 3 | Non Fair Value Option Held For Sale Loans [Member]
Financial assets:
Loans held for sale		25		384
Total Fair Value | Fair Value, Inputs, Level 3 | Commercial and Industrial Loans | Commercial
Financial assets:
Portfolio loans and leases at fair value		43,981		41,802
Total Fair Value | Fair Value, Inputs, Level 3 | Commercial Mortgage Loans | Commercial
Financial assets:
Portfolio loans and leases, net		6,692		6,656
Total Fair Value | Fair Value, Inputs, Level 3 | Commercial Construction Loans | Commercial
Financial assets:
Portfolio loans and leases, net		3,436		2,918
Total Fair Value | Fair Value, Inputs, Level 3 | Commercial Leases | Commercial
Financial assets:
Portfolio loans and leases, net		3,739		3,533
Total Fair Value | Fair Value, Inputs, Level 3 | Residential Mortgage
Financial assets:
Portfolio loans and leases at fair value		14,937		14,061
Total Fair Value | Fair Value, Inputs, Level 3 | Home Equity
Financial assets:
Portfolio loans and leases at fair value		8,790		8,948
Total Fair Value | Fair Value, Inputs, Level 3 | Automobile Loan [Member]
Financial assets:
Portfolio loans and leases at fair value		10,392		11,170
Total Fair Value | Fair Value, Inputs, Level 3 | Credit Card Receivables [Member]
Financial assets:
Portfolio loans and leases at fair value		2,437		2,551
Total Fair Value | Fair Value, Inputs, Level 3 | Other Consumer Loans and Leases
Financial assets:
Portfolio loans and leases, net		$ 649		$ 643

[1] Includes $ 128 and $ 152 of cash and due from banks, $ 1,853 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 $ 1,744 and $ 2,487 of long-term debt from consolidated VIEs that are included in their respective captions above at June 30, 2016 and December 31, 2015 , respectively. For further information refer to Note 9 .

[2] Fair value of $ 62 and $ 70 at June 30, 2016 and December 31, 2015 , respectively.

[3] Includes $ 852 and $ 519 of residential mortgage loans held for sale measured at fair value at June 30, 2016 and December 31, 2015 , respectively.

[4] Amortized cost of $ 30,101 and $ 28,678 at June 30, 2016 and Dec ember 31, 2015 , respectively.

[5] Includes $ 0 and $ 628 of deposits held for sale at June 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 million of debt issuance costs from other assets to long-term debt. For further information refer to Note 3.