Carrying Amounts and Estimated Fair Values for Certain Financial Instruments (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013		Mar. 31, 2013	Dec. 31, 2012
Financial assets:
Cash and due from banks	$ 3,153	[1]	$ 3,178	[1]	$ 2,186	$ 2,441
Held-to-maturity securities	195	[2]	208	[2]
Other short-term investments	2,202	[1]	5,116	[1]
Loans held for sale	780	[3]	944	[3]
Portfolio loans and leases, net	88,222		87,032
Other securities, fair value	20,749	[4]	18,597	[4]
Held-to-maturity securities, fair value	195		208
Loans held for sale	649		890
Financial liabilities:
Deposits	96,874		99,275
Federal funds purchased	268		284
Other short-term borrowings	2,717		1,380
Long-term debt	11,233	[1]	9,633	[1]
Carrying (Reported) Amount, Fair Value Disclosure
Financial assets:
Cash and due from banks	3,153		3,178
Held-to-maturity securities	195		208
Other short-term investments	2,202		5,116
Unallocated Allowance For Loan And Lease Losses	(105)		(110)
Portfolio loans and leases at fair value	88,119		86,940
Financial liabilities:
Deposits	96,874		99,275
Federal funds purchased	268		284
Other short-term borrowings	2,717		1,380
Long-term debt	11,233		9,633
Carrying (Reported) Amount, Fair Value Disclosure | Non Fair Value Option Held For Sale Loans [Member]
Financial assets:
Loans held for sale	131		54
Carrying (Reported) Amount, Fair Value Disclosure | FHLB and FRB restricted stock holdings
Financial assets:
Other securities	599		751
Carrying (Reported) Amount, Fair Value Disclosure | Commercial And Industrial Loans [Member]
Financial assets:
Portfolio loans and leases, net	39,872		38,549
Carrying (Reported) Amount, Fair Value Disclosure | Commercial Mortgage Loans [Member]
Financial assets:
Portfolio loans and leases, net	7,767		7,854
Carrying (Reported) Amount, Fair Value Disclosure | Commercial Construction
Financial assets:
Portfolio loans and leases, net	1,195		1,013
Carrying (Reported) Amount, Fair Value Disclosure | Commercial Leases [Member]
Financial assets:
Portfolio loans and leases, net	3,529		3,572
Carrying (Reported) Amount, Fair Value Disclosure | Residential Mortgage
Financial assets:
Portfolio loans and leases, net	12,343		12,399
Carrying (Reported) Amount, Fair Value Disclosure | Home Equity
Financial assets:
Portfolio loans and leases, net	9,039		9,152
Carrying (Reported) Amount, Fair Value Disclosure | Automobile Loan
Financial assets:
Portfolio loans and leases, net	12,060		11,961
Carrying (Reported) Amount, Fair Value Disclosure | Credit Card Loan [Member]
Financial assets:
Portfolio loans and leases, net	2,087		2,202
Carrying (Reported) Amount, Fair Value Disclosure | Other Consumer Loans And Leases [Member]
Financial assets:
Portfolio loans and leases, net	332		348
Portion at Fair Value, Fair Value Disclosure
Financial assets:
Cash and due from banks, fair value	3,153		3,178
Other securities, fair value	599		751
Held-to-maturity securities, fair value	195		208
Other short term investments, fair value	2,202		5,116
Portfolio loans and leases at fair value	88,187		86,562
Financial liabilities:
Deposits, fair value	96,893		99,288
Federal funds purchased, fair value	268		284
Other short-term borrowings, fair value	2,718		1,380
Long term debt, fair value	11,863		10,222
Portion at Fair Value, Fair Value Disclosure | Non Fair Value Option Held For Sale Loans [Member]
Financial assets:
Loans held for sale	131		54
Portion at Fair Value, Fair Value Disclosure | Commercial And Industrial Loans [Member]
Financial assets:
Portfolio loans and leases at fair value	41,192		39,804
Portion at Fair Value, Fair Value Disclosure | Commercial Mortgage Loans [Member]
Financial assets:
Portfolio loans and leases at fair value	7,365		7,430
Portion at Fair Value, Fair Value Disclosure | Commercial Construction
Financial assets:
Portfolio loans and leases at fair value	1,015		856
Portion at Fair Value, Fair Value Disclosure | Commercial Leases [Member]
Financial assets:
Portfolio loans and leases at fair value	3,270		3,261
Portion at Fair Value, Fair Value Disclosure | Residential Mortgage
Financial assets:
Portfolio loans and leases at fair value	11,841		11,541
Portion at Fair Value, Fair Value Disclosure | Home Equity
Financial assets:
Portfolio loans and leases at fair value	9,081		9,181
Portion at Fair Value, Fair Value Disclosure | Automobile Loan
Financial assets:
Portfolio loans and leases at fair value	11,818		11,748
Portion at Fair Value, Fair Value Disclosure | Credit Card Loan [Member]
Financial assets:
Portfolio loans and leases at fair value	2,263		2,380
Portion at Fair Value, Fair Value Disclosure | Other Consumer Loans And Leases [Member]
Financial assets:
Portfolio loans and leases at fair value	342		361
Portion at Fair Value, Fair Value Disclosure | Fair Value, Inputs, Level 1
Financial assets:
Cash and due from banks, fair value	3,153		3,178
Other short term investments, fair value	2,202		5,116
Financial liabilities:
Federal funds purchased, fair value	268		284
Long term debt, fair value	11,257		9,645
Portion at Fair Value, Fair Value Disclosure | Fair Value, Inputs, Level 2
Financial liabilities:
Deposits, fair value	96,893		99,288
Other short-term borrowings, fair value	2,718		1,380
Long term debt, fair value	606		577
Portion at Fair Value, Fair Value Disclosure | Fair Value, Inputs, Level 2 | FHLB and FRB restricted stock holdings
Financial assets:
Other securities, fair value	599		751
Portion at Fair Value, Fair Value Disclosure | Fair Value, Inputs, Level 3
Financial assets:
Held-to-maturity securities, fair value	195		208
Portfolio loans and leases at fair value	88,187		86,562
Portion at Fair Value, Fair Value Disclosure | Fair Value, Inputs, Level 3 | Non Fair Value Option Held For Sale Loans [Member]
Financial assets:
Loans held for sale	131		54
Portion at Fair Value, Fair Value Disclosure | Fair Value, Inputs, Level 3 | Commercial And Industrial Loans [Member]
Financial assets:
Portfolio loans and leases at fair value	41,192		39,804
Portion at Fair Value, Fair Value Disclosure | Fair Value, Inputs, Level 3 | Commercial Mortgage Loans [Member]
Financial assets:
Portfolio loans and leases at fair value	7,365		7,430
Portion at Fair Value, Fair Value Disclosure | Fair Value, Inputs, Level 3 | Commercial Construction
Financial assets:
Portfolio loans and leases at fair value	1,015		856
Portion at Fair Value, Fair Value Disclosure | Fair Value, Inputs, Level 3 | Commercial Leases [Member]
Financial assets:
Portfolio loans and leases at fair value	3,270		3,261
Portion at Fair Value, Fair Value Disclosure | Fair Value, Inputs, Level 3 | Residential Mortgage
Financial assets:
Portfolio loans and leases at fair value	11,841		11,541
Portion at Fair Value, Fair Value Disclosure | Fair Value, Inputs, Level 3 | Home Equity
Financial assets:
Portfolio loans and leases at fair value	9,081		9,181
Portion at Fair Value, Fair Value Disclosure | Fair Value, Inputs, Level 3 | Automobile Loan
Financial assets:
Portfolio loans and leases at fair value	11,818		11,748
Portion at Fair Value, Fair Value Disclosure | Fair Value, Inputs, Level 3 | Credit Card Loan [Member]
Financial assets:
Portfolio loans and leases at fair value	2,263		2,380
Portion at Fair Value, Fair Value Disclosure | Fair Value, Inputs, Level 3 | Other Consumer Loans And Leases [Member]
Financial assets:
Portfolio loans and leases at fair value	$ 342		$ 361

[1] Includes $102 and $49 of cash and due from banks, $7 and $0 of other short-term investments, $48 and $48 of commercial mortgage loans, $2,031 and $1,010 of automobile loans, $(18) and $(15) of ALLL, $23 and $13 of other assets, $3 and $1 of other liabilities, and $2,119 and $1,048 of long-term debt from consolidated VIEs that are included in their respective captions above at March 31, 2014 and December 31, 2013, respectively. See Note 8.

[2] Fair value of $195 and $208 at March 31, 2014 and December 31, 2013, respectively.

[3] Includes $649 and $890 of residential mortgage loans held for sale measured at fair value at March 31, 2014 and December 31, 2013, respectively.

[4] Amortized cost of $20,393 and $18,409 at March 31, 2014 and December 31, 2013, respectively.