Carrying Amounts and Estimated Fair Values for Certain Financial Instruments (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010	Dec. 31, 2009
Financial assets:
Cash and due from banks	$ 2,441	[1]	$ 2,663	[1]	$ 2,159	$ 2,318
Held-to-maturity securities	284		322
Other short-term investments	2,421	[1]	1,781	[1]
Loans held for sale	2,856		2,751
Portfolio loans and leases:
Commercial and industrial loans	36,038		30,783
Commercial mortgage loans	9,103	[1]	10,138	[1]
Commercial construction loans	698		1,020
Commercial leases	3,549		3,531
Residential mortgage loans	12,017	[2]	10,672	[2]
Home equity	10,018	[1]	10,719	[1]
Automobile loans	11,972	[1]	11,827	[1]
Credit card	2,097		1,978
Other consumer loans and leases	290		350
Financial liabilities:
Federal funds purchased	901		346
Fair Value, Inputs, Level 1
Financial assets:
Cash and due from banks	2,441
Other short-term investments	2,421
Financial liabilities:
Federal funds purchased	901
Long-term debt	6,925
Fair Value, Inputs, Level 2
Financial assets:
Other securities	844
Financial liabilities:
Deposits	89,592
Other short-term borrowings	6,280
Long-term debt	884
Fair Value, Inputs, Level 3
Financial assets:
Held-to-maturity securities	284
Loans held for sale	83
Portfolio loans and leases:
Commercial and industrial loans	36,496
Commercial mortgage loans	8,020
Commercial construction loans	505
Commercial leases	3,310
Residential mortgage loans	11,532
Home equity	9,798
Automobile loans	12,076
Credit card	2,139
Other consumer loans and leases	288
Total portfolio loans and leases, net	84,164
Carrying (Reported) Amount, Fair Value Disclosure
Financial assets:
Cash and due from banks	2,441		2,663
Other securities	844		842
Held-to-maturity securities	284		322
Other short-term investments	2,421		1,781
Loans held for sale	83		203
Portfolio loans and leases:
Commercial and industrial loans	35,236		29,854
Commercial mortgage loans	8,770		9,697
Commercial construction loans	665		943
Commercial leases	3,481		3,451
Residential mortgage loans	11,712	[3]	10,380	[4]
Home equity	9,875		10,524
Automobile loans	11,944		11,784
Credit card	2,010		1,872
Other consumer loans and leases	270		329
Unallocated allowance for loan and lease losses	(111)		(136)
Total portfolio loans and leases, net	83,852	[3]	78,698	[4]
Financial liabilities:
Deposits	89,517		85,710
Federal funds purchased	901		346
Other short-term borrowings	6,280		3,239
Long-term debt	7,085		9,682
Portion at Fair Value, Fair Value Disclosure
Financial assets:
Cash and due from banks	2,441		2,663
Other securities	844		842
Held-to-maturity securities	284		322
Other short-term investments	2,421		1,781
Loans held for sale	83		203
Portfolio loans and leases:
Commercial and industrial loans	36,496		30,300
Commercial mortgage loans	8,020		8,870
Commercial construction loans	505		791
Commercial leases	3,310		3,237
Residential mortgage loans	11,532	[3]	9,978	[4]
Home equity	9,798		9,737
Automobile loans	12,076		11,747
Credit card	2,139		1,958
Other consumer loans and leases	288		346
Total portfolio loans and leases, net	84,164	[3]	76,964	[4]
Financial liabilities:
Deposits	89,592		85,599
Federal funds purchased	901		346
Other short-term borrowings	6,280		3,239
Long-term debt	$ 7,809		$ 10,197

[1] At December 31, 2012 and 2011, includes $0 and $30 of cash, $0 and $7 of other short-term investments, $50 and $50 of commercial mortgage loans, $0 and $223 of home equity loans, $0 and $259 of automobile loans, ($5) and ($10) of ALLL, $3 and $4 of other assets, $0 and $4 of other liabilities, $0 and $191 of long-term debt from consolidated VIEs that are included in their respective captions. See Note 10.

[2] Includes $76 and $65 of residential mortgage loans measured at fair value at December 31, 2012 and 2011, respectively.

[3] Excludes $76 of residential mortgage loans measured at fair value on a recurring basis.

[4] Excludes $65 of residential mortgage loans measured at fair value on a recurring basis.