Carrying Amounts and Estimated Fair Values for Certain Financial Instruments (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012		Dec. 31, 2011		Jun. 30, 2011		Dec. 31, 2010
Financial assets:
Cash and due from banks	$ 2,393	[1]	$ 2,663	[1]	$ 2,380	[1]	$ 2,159
Other short-term investments	1,964	[1]	1,781	[1]	1,370	[1]
Loans held for sale	1,788		2,751		978
Portfolio loans and leases:
Commercial and industrial loans	32,612		30,783		28,099
Commercial mortgage loans	9,662	[1]	10,138	[1]	10,233	[1]
Commercial construction loans	822		1,020		1,778
Commercial leases	3,467		3,531		3,326
Residential mortgage loans	11,429	[2]	10,672	[2]	9,849	[2]
Home equity	10,377	[1]	10,719	[1]	11,048	[1]
Automobile loans	11,739	[1]	11,827	[1]	11,315	[1]
Credit card	1,943		1,978		1,856
Other consumer loans and leases	308		350		463
Financial liabilities:
Federal funds purchased	641		346		403
Fair Value, Inputs, Level 2
Financial assets:
Loans held for sale	1,788		2,751		978
Carrying (Reported) Amount, Fair Value Disclosure
Financial assets:
Cash and due from banks	2,393		2,663		2,380
Other securities	843		842		841
Held-to-maturity securities	305		322		344
Other short-term investments	1,964		1,781		1,370
Loans held for sale	75		203		207
Portfolio loans and leases:
Commercial and industrial loans	31,771		29,854		27,022
Commercial mortgage loans	9,279		9,697		9,748
Commercial construction loans	773		943		1,670
Commercial leases	3,393		3,451		3,232
Residential mortgage loans	11,121	[3]	10,380	[4]	9,522
Home equity	10,208		10,524		10,817
Automobile loans	11,702		11,784		11,254
Credit card	1,853		1,872		1,720
Other consumer loans and leases	288		329		439
Unallocated allowance for loan and lease losses	(121)		(136)		(130)
Total portfolio loans and leases, net	80,267	[3]	78,698	[4]	75,294
Financial liabilities:
Deposits	84,273		85,710		80,598
Federal funds purchased	641		346		403
Other short-term borrowings	4,613		3,239		2,702
Long-term debt	9,685		9,682		10,152
Portion at Fair Value, Fair Value Disclosure
Financial assets:
Cash and due from banks	2,393		2,663		2,380
Other securities	843		842		841
Held-to-maturity securities	305		322		344
Other short-term investments	1,964		1,781		1,370
Loans held for sale	75		203		207
Portfolio loans and leases:
Commercial and industrial loans	32,928		30,300		28,447
Commercial mortgage loans	8,519		8,870		9,252
Commercial construction loans	622		791		1,328
Commercial leases	3,283		3,237		2,917
Residential mortgage loans	11,144	[3]	9,978	[4]	8,617	[5]
Home equity	9,917		9,737		9,660
Automobile loans	11,672		11,747		11,301
Credit card	1,999		1,958		1,795
Other consumer loans and leases	305		346		482
Total portfolio loans and leases, net	80,389	[3]	76,964	[4]	73,799	[5]
Financial liabilities:
Deposits	84,385		85,599		80,770
Federal funds purchased	641		346		403
Other short-term borrowings	4,613		3,239		2,702
Long-term debt	10,411		10,197		10,675
Portion at Fair Value, Fair Value Disclosure | Fair Value, Inputs, Level 1
Financial assets:
Cash and due from banks	2,393
Other short-term investments	1,964
Financial liabilities:
Federal funds purchased	641
Long-term debt	8,314
Portion at Fair Value, Fair Value Disclosure | Fair Value, Inputs, Level 2
Financial assets:
Other securities	843
Financial liabilities:
Deposits	84,385
Other short-term borrowings	4,613
Long-term debt	2,097
Portion at Fair Value, Fair Value Disclosure | Fair Value, Inputs, Level 3
Financial assets:
Held-to-maturity securities	305
Loans held for sale	75
Portfolio loans and leases:
Commercial and industrial loans	32,928
Commercial mortgage loans	8,519
Commercial construction loans	622
Commercial leases	3,283
Residential mortgage loans	11,144
Home equity	9,917
Automobile loans	11,672
Credit card	1,999
Other consumer loans and leases	305
Total portfolio loans and leases, net	$ 80,389

[1] Includes $9, $30 and $42 of cash, $4, $7 and $7of other short-term investments, $51, $50 and $29 of commercial mortgage loans, $0, $223 and $231 of home equity loans, $75, $259 and $424 of automobile loans, ($3), ($10) and ($11) of ALLL, $3, $4 and $4 of other assets, $2, $4 and $8 of other liabilities, $73, $191and $365 of long-term debt from consolidated VIEs that are included in their respective captions above at June 30, 2012, December 31, 2011 and June 30, 2011, respectively. See Note 8.

[2] Includes $76, $65 and $59 of residential mortgage loans measured at fair value at June 30, 2012, December 31, 2011 and June 30, 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.

[5] (a) Excludes $59 million of residential mortgage loans measured at fair value on a recurring basis.