Carrying Amounts and Estimated Fair Values for Certain Financial Instruments (Detail) - USD ($) $ in Millions		Jun. 30, 2015		Dec. 31, 2014		Jun. 30, 2014	Dec. 31, 2013
Financial assets:
Cash and due from banks		$ 2,785	[1]	$ 3,091	[1]	$ 3,312	$ 3,178
Held-to-maturity securities, amortized cost	[2]	157		187
Other short-term investments		3,451		7,914
Loans held for sale	[3]	995		1,261
Portfolio loans and leases, net		91,410		88,762
Other securities, fair value	[4]	27,987		22,408
Held-to-maturity securities, fair value		157		187
Loans held for sale		628		561
Financial liabilities:
Deposits	[5]	103,023		101,712
Federal funds purchased		126		144
Other short-term borrowings		4,136		1,556
Long-term debt	[1]	13,521		14,967
Residential Mortgage
Financial assets:
Portfolio loans and leases at fair value		178				$ 99
Carrying (Reported) Amount, Fair Value Disclosure
Financial assets:
Cash and due from banks		2,785		3,091
Held-to-maturity securities, amortized cost		157		187
Other short-term investments		3,451		7,914
Unallocated Allowance For Loan And Lease Losses		(103)		(106)
Portfolio loans and leases at fair value		91,232		88,654
Financial liabilities:
Deposits		103,023		101,712
Federal funds purchased		126		144
Other short-term borrowings		4,136		1,556
Long-term debt		13,521		14,967
Carrying (Reported) Amount, Fair Value Disclosure | Non Fair Value Option Held For Sale Loans [Member]
Financial assets:
Loans held for sale		367		700
Carrying (Reported) Amount, Fair Value Disclosure | FHLB and FRB restricted stock holdings
Financial assets:
Other securities		601		600
Carrying (Reported) Amount, Fair Value Disclosure | Commercial and Industrial Loans
Financial assets:
Portfolio loans and leases, net		42,132		40,092
Carrying (Reported) Amount, Fair Value Disclosure | Commercial Mortgage Loans
Financial assets:
Portfolio loans and leases, net		7,033		7,259
Carrying (Reported) Amount, Fair Value Disclosure | Commercial Construction
Financial assets:
Portfolio loans and leases, net		2,687		2,052
Carrying (Reported) Amount, Fair Value Disclosure | Commercial Leases
Financial assets:
Portfolio loans and leases, net		3,833		3,675
Carrying (Reported) Amount, Fair Value Disclosure | Residential Mortgage
Financial assets:
Portfolio loans and leases, net		12,651		12,177
Carrying (Reported) Amount, Fair Value Disclosure | Home Equity
Financial assets:
Portfolio loans and leases, net		8,470		8,799
Carrying (Reported) Amount, Fair Value Disclosure | Automobile Loan Securitizations
Financial assets:
Portfolio loans and leases, net		11,867		12,004
Carrying (Reported) Amount, Fair Value Disclosure | Credit Card Loan [Member]
Financial assets:
Portfolio loans and leases, net		2,180		2,297
Carrying (Reported) Amount, Fair Value Disclosure | Other Consumer Loans and Leases
Financial assets:
Portfolio loans and leases, net		482		405
Portion at Fair Value
Financial assets:
Cash and due from banks, fair value		2,785		3,091
Held-to-maturity securities, fair value		157		187
Other short term investments, fair value		3,451		7,914
Portfolio loans and leases at fair value		92,317		89,041
Financial liabilities:
Deposits, fair value		103,026		101,715
Federal funds purchased, fair value		126		144
Other short-term borrowings, fair value		4,138		1,561
Long term debt, fair value		14,074		15,648
Portion at Fair Value | Non Fair Value Option Held For Sale Loans [Member]
Financial assets:
Loans held for sale		367		700
Portion at Fair Value | FHLB and FRB restricted stock holdings
Financial assets:
Other securities, fair value		601		600
Portion at Fair Value | Commercial and Industrial Loans
Financial assets:
Portfolio loans and leases at fair value		42,873		40,781
Portion at Fair Value | Commercial Mortgage Loans
Financial assets:
Portfolio loans and leases at fair value		6,791		6,878
Portion at Fair Value | Commercial Construction
Financial assets:
Portfolio loans and leases at fair value		2,436		1,735
Portion at Fair Value | Commercial Leases
Financial assets:
Portfolio loans and leases at fair value		3,569		3,426
Portion at Fair Value | Residential Mortgage
Financial assets:
Portfolio loans and leases at fair value		12,923		12,249
Portion at Fair Value | Home Equity
Financial assets:
Portfolio loans and leases at fair value		9,091		9,224
Portion at Fair Value | Automobile Loan Securitizations
Financial assets:
Portfolio loans and leases at fair value		11,636		11,748
Portion at Fair Value | Credit Card Loan [Member]
Financial assets:
Portfolio loans and leases at fair value		2,508		2,586
Portion at Fair Value | Other Consumer Loans and Leases
Financial assets:
Portfolio loans and leases at fair value		490		414
Portion at Fair Value | Fair Value, Inputs, Level 1
Financial assets:
Cash and due from banks, fair value		2,785		3,091
Other short term investments, fair value		3,451		7,914
Financial liabilities:
Federal funds purchased, fair value		126		144
Long term debt, fair value		13,471		14,993
Portion at Fair Value | Fair Value, Inputs, Level 2
Financial liabilities:
Deposits, fair value		103,026		101,715
Other short-term borrowings, fair value		4,138		1,561
Long term debt, fair value		603		655
Portion at Fair Value | Fair Value, Inputs, Level 2 | FHLB and FRB restricted stock holdings
Financial assets:
Other securities, fair value		601		600
Portion at Fair Value | Fair Value, Inputs, Level 3
Financial assets:
Held-to-maturity securities, fair value		157		187
Portfolio loans and leases at fair value		92,317		89,041
Portion at Fair Value | Fair Value, Inputs, Level 3 | Non Fair Value Option Held For Sale Loans [Member]
Financial assets:
Loans held for sale		367		700
Portion at Fair Value | Fair Value, Inputs, Level 3 | Commercial and Industrial Loans
Financial assets:
Portfolio loans and leases at fair value		42,873		40,781
Portion at Fair Value | Fair Value, Inputs, Level 3 | Commercial Mortgage Loans
Financial assets:
Portfolio loans and leases at fair value		6,791		6,878
Portion at Fair Value | Fair Value, Inputs, Level 3 | Commercial Construction
Financial assets:
Portfolio loans and leases at fair value		2,436		1,735
Portion at Fair Value | Fair Value, Inputs, Level 3 | Commercial Leases
Financial assets:
Portfolio loans and leases at fair value		3,569		3,426
Portion at Fair Value | Fair Value, Inputs, Level 3 | Residential Mortgage
Financial assets:
Portfolio loans and leases at fair value		12,923		12,249
Portion at Fair Value | Fair Value, Inputs, Level 3 | Home Equity
Financial assets:
Portfolio loans and leases at fair value		9,091		9,224
Portion at Fair Value | Fair Value, Inputs, Level 3 | Automobile Loan Securitizations
Financial assets:
Portfolio loans and leases at fair value		11,636		11,748
Portion at Fair Value | Fair Value, Inputs, Level 3 | Credit Card Loan [Member]
Financial assets:
Portfolio loans and leases at fair value		2,508		2,586
Portion at Fair Value | Fair Value, Inputs, Level 3 | Other Consumer Loans and Leases
Financial assets:
Portfolio loans and leases at fair value		$ 490		$ 414

[1] Includes $156 and $179 of cash and due from banks, $2,547 and $3,378 of portfolio loans and leases, $(29) and $(22) of ALLL, $23 and $25 of other assets, $4 and $5 of other liabilities, and $2,542 and $3,434 of long-term debt from consolidated VIEs that are included in their respective captions above at June 30, 2015 and December 31, 2014, respectively. For further information refer to Note 10.

[2] Fair value of $157 and $187 at June 30, 2015 and December 31, 2014, respectively.

[3] Includes $628 and $561 of residential mortgage loans held for sale measured at fair value at June 30, 2015 and December 31, 2014, respectively.

[4] Amortized cost of $27,483 and $21,677 at June 30, 2015 and December 31, 2014, respectively.

[5] Includes $561 and $0 of deposits held for sale at June 30, 2015 and December 31, 2014, respectively.