Carrying Amounts and Estimated Fair Values for Certain Financial Instruments (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014		Dec. 31, 2013		Sep. 30, 2013	Dec. 31, 2012
Financial assets:
Cash and due from banks	$ 3,125	[1]	$ 3,178	[1]	$ 2,887	$ 2,441
Held-to-maturity securities, amortized cost	191	[2]	208	[2]
Other short-term investments	3,637		5,116
Loans held for sale	641	[3]	944	[3]
Portfolio loans and leases, net	89,210		87,032
Other securities, fair value	22,912	[4]	18,597	[4]
Held-to-maturity securities, fair value	191		208
Loans held for sale	579		890
Financial liabilities:
Deposits	97,292		99,275
Federal funds purchased	148		284
Other short-term borrowings	2,730		1,380
Long-term debt	14,336	[1]	9,633	[1]
Residential Mortgage
Financial assets:
Portfolio loans and leases at fair value	109				89
Carrying (Reported) Amount, Fair Value Disclosure
Financial assets:
Cash and due from banks	3,125		3,178
Held-to-maturity securities, amortized cost	191		208
Other short-term investments	3,637		5,116
Unallocated Allowance For Loan And Lease Losses	(99)		(110)
Portfolio loans and leases at fair value	89,101		86,940
Financial liabilities:
Deposits	97,292		99,275
Federal funds purchased	148		284
Other short-term borrowings	2,730		1,380
Long-term debt	14,336		9,633
Carrying (Reported) Amount, Fair Value Disclosure | Non Fair Value Option Held For Sale Loans [Member]
Financial assets:
Loans held for sale	62		54
Carrying (Reported) Amount, Fair Value Disclosure | FHLB and FRB restricted stock holdings
Financial assets:
Other securities	600		751
Carrying (Reported) Amount, Fair Value Disclosure | Commercial and Industrial Loans
Financial assets:
Portfolio loans and leases, net	40,372		38,549
Carrying (Reported) Amount, Fair Value Disclosure | Commercial Mortgage Loans
Financial assets:
Portfolio loans and leases, net	7,414		7,854
Carrying (Reported) Amount, Fair Value Disclosure | Commercial Construction
Financial assets:
Portfolio loans and leases, net	1,687		1,013
Carrying (Reported) Amount, Fair Value Disclosure | Commercial Leases
Financial assets:
Portfolio loans and leases, net	3,506		3,572
Carrying (Reported) Amount, Fair Value Disclosure | Residential Mortgage
Financial assets:
Portfolio loans and leases, net	12,668		12,399
Carrying (Reported) Amount, Fair Value Disclosure | Home Equity
Financial assets:
Portfolio loans and leases, net	8,896		9,152
Carrying (Reported) Amount, Fair Value Disclosure | Automobile Loan Securitizations
Financial assets:
Portfolio loans and leases, net	12,091		11,961
Carrying (Reported) Amount, Fair Value Disclosure | Credit Card Loan [Member]
Financial assets:
Portfolio loans and leases, net	2,216		2,202
Carrying (Reported) Amount, Fair Value Disclosure | Other Consumer Loans and Leases
Financial assets:
Portfolio loans and leases, net	350		348
Portion at Fair Value
Financial assets:
Cash and due from banks, fair value	3,125		3,178
Held-to-maturity securities, fair value	191		208
Other short term investments, fair value	3,637		5,116
Portfolio loans and leases at fair value	88,779		86,562
Financial liabilities:
Deposits, fair value	97,296		99,288
Federal funds purchased, fair value	148		284
Other short-term borrowings, fair value	2,733		1,380
Long term debt, fair value	14,989		10,222
Portion at Fair Value | Non Fair Value Option Held For Sale Loans [Member]
Financial assets:
Loans held for sale	62		54
Portion at Fair Value | FHLB and FRB restricted stock holdings
Financial assets:
Other securities, fair value	600		751
Portion at Fair Value | Commercial and Industrial Loans
Financial assets:
Portfolio loans and leases at fair value	41,228		39,804
Portion at Fair Value | Commercial Mortgage Loans
Financial assets:
Portfolio loans and leases at fair value	7,017		7,430
Portion at Fair Value | Commercial Construction
Financial assets:
Portfolio loans and leases at fair value	1,408		856
Portion at Fair Value | Commercial Leases
Financial assets:
Portfolio loans and leases at fair value	3,230		3,261
Portion at Fair Value | Residential Mortgage
Financial assets:
Portfolio loans and leases at fair value	12,243		11,541
Portion at Fair Value | Home Equity
Financial assets:
Portfolio loans and leases at fair value	8,999		9,181
Portion at Fair Value | Automobile Loan Securitizations
Financial assets:
Portfolio loans and leases at fair value	11,817		11,748
Portion at Fair Value | Credit Card Loan [Member]
Financial assets:
Portfolio loans and leases at fair value	2,475		2,380
Portion at Fair Value | Other Consumer Loans and Leases
Financial assets:
Portfolio loans and leases at fair value	362		361
Portion at Fair Value | Fair Value, Inputs, Level 1
Financial assets:
Cash and due from banks, fair value	3,125		3,178
Other short term investments, fair value	3,637		5,116
Financial liabilities:
Federal funds purchased, fair value	148		284
Long term debt, fair value	14,405		9,645
Portion at Fair Value | Fair Value, Inputs, Level 2
Financial liabilities:
Deposits, fair value	97,296		99,288
Other short-term borrowings, fair value	2,733		1,380
Long term debt, fair value	584		577
Portion at Fair Value | Fair Value, Inputs, Level 2 | FHLB and FRB restricted stock holdings
Financial assets:
Other securities, fair value	600		751
Portion at Fair Value | Fair Value, Inputs, Level 3
Financial assets:
Held-to-maturity securities, fair value	191		208
Portfolio loans and leases at fair value	88,779		86,562
Portion at Fair Value | Fair Value, Inputs, Level 3 | Non Fair Value Option Held For Sale Loans [Member]
Financial assets:
Loans held for sale	62		54
Portion at Fair Value | Fair Value, Inputs, Level 3 | Commercial and Industrial Loans
Financial assets:
Portfolio loans and leases at fair value	41,228		39,804
Portion at Fair Value | Fair Value, Inputs, Level 3 | Commercial Mortgage Loans
Financial assets:
Portfolio loans and leases at fair value	7,017		7,430
Portion at Fair Value | Fair Value, Inputs, Level 3 | Commercial Construction
Financial assets:
Portfolio loans and leases at fair value	1,408		856
Portion at Fair Value | Fair Value, Inputs, Level 3 | Commercial Leases
Financial assets:
Portfolio loans and leases at fair value	3,230		3,261
Portion at Fair Value | Fair Value, Inputs, Level 3 | Residential Mortgage
Financial assets:
Portfolio loans and leases at fair value	12,243		11,541
Portion at Fair Value | Fair Value, Inputs, Level 3 | Home Equity
Financial assets:
Portfolio loans and leases at fair value	8,999		9,181
Portion at Fair Value | Fair Value, Inputs, Level 3 | Automobile Loan Securitizations
Financial assets:
Portfolio loans and leases at fair value	11,817		11,748
Portion at Fair Value | Fair Value, Inputs, Level 3 | Credit Card Loan [Member]
Financial assets:
Portfolio loans and leases at fair value	2,475		2,380
Portion at Fair Value | Fair Value, Inputs, Level 3 | Other Consumer Loans and Leases
Financial assets:
Portfolio loans and leases at fair value	$ 362		$ 361

[1] Includes $150 and $49 of cash and due from banks, $48 and $48 of commercial mortgage loans, $2,785 and $1,010 of automobile loans, $(19) and $(15) of ALLL, $26 and $13 of other assets, $7 and $1 of other liabilities, and $2,882 and $1,048 of long-term debt from consolidated VIEs that are included in their respective captions above at September 30, 2014 and December 31, 2013, respectively. See Note 10.

[2] Fair value of $191 and $208 at September 30, 2014 and December 31, 2013, respectively.

[3] Includes $579 and $890 of residential mortgage loans held for sale measured at fair value at September 30, 2014 and December 31, 2013, respectively.

[4] Amortized cost of $22,392 and $18,409 at September 30, 2014 and December 31, 2013, respectively.