Carrying Amounts and Estimated Fair Values for Certain Financial Instruments (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012		Dec. 31, 2011		Mar. 31, 2011		Dec. 31, 2010
Financial assets:
Cash and due from banks	$ 2,235	[1]	$ 2,663	[1]	$ 2,121	[1]	$ 2,159
Held-to-maturity securities	321		322		346
Other short-term investments	1,628	[1]	1,781	[1]	2,481	[1]
Loans held for sale	1,429		2,751		1,017
Portfolio loans and leases:
Commercial and industrial loans	32,155		30,783		27,344
Commercial mortgage loans	9,909	[1]	10,138	[1]	10,510	[1]
Commercial construction loans	901		1,020		1,980
Commercial leases	3,512		3,531		3,367
Residential mortgage loans	11,094	[2]	10,672	[2]	9,530	[2]
Home equity	10,493	[1]	10,719	[1]	11,222	[1]
Automobile loans	11,832	[1]	11,827	[1]	11,129	[1]
Credit card	1,896		1,978		1,821
Other consumer loans and leases	321		350		562
Financial liabilities:
Federal funds purchased	319		346		332
Fair Value, Inputs, Level 2
Financial assets:
Loans held for sale	1,429		2,751		1,017
Carrying (Reported) Amount, Fair Value Disclosure
Financial assets:
Cash and due from banks	2,235		2,663		2,121
Other securities	842		842		868
Held-to-maturity securities	321		322		346
Other short-term investments	1,628		1,781		2,481
Loans held for sale	155		203		274
Portfolio loans and leases:
Commercial and industrial loans	31,269		29,854		26,251
Commercial mortgage loans	9,507		9,697		9,984
Commercial construction loans	838		943		1,840
Commercial leases	3,439		3,451		3,271
Residential mortgage loans	10,794	[3]	10,380	[4]	9,190
Home equity	10,309		10,524		10,981
Automobile loans	11,792		11,784		11,059
Credit card	1,798		1,872		1,668
Other consumer loans and leases	302		329		507
Unallocated allowance for loan and lease losses	(128)		(136)		(145)
Total portfolio loans and leases, net	79,920	[3]	78,698	[4]	74,606
Financial liabilities:
Deposits	85,791		85,710		82,317
Federal funds purchased	319		346		332
Other short-term borrowings	2,877		3,239		1,297
Long-term debt	9,648		9,682		10,555
Portion at Fair Value, Fair Value Disclosure
Financial assets:
Cash and due from banks	2,235		2,663		2,121
Other securities	842		842		868
Held-to-maturity securities	321		322		346
Other short-term investments	1,628		1,781		2,481
Loans held for sale	155		203		274
Portfolio loans and leases:
Commercial and industrial loans	32,075		30,300		27,690
Commercial mortgage loans	8,697		8,870		9,053
Commercial construction loans	689		791		1,309
Commercial leases	3,203		3,237		2,926
Residential mortgage loans	10,627	[3]	9,978	[4]	8,250
Home equity	9,866		9,737		9,575
Automobile loans	11,755		11,747		11,077
Credit card	1,903		1,958		1,771
Other consumer loans and leases	319		346		559
Total portfolio loans and leases, net	79,134	[3]	76,964	[4]	72,210
Financial liabilities:
Deposits	85,912		85,599		82,511
Federal funds purchased	319		346		332
Other short-term borrowings	2,877		3,239		1,297
Long-term debt	10,166		10,197		11,088
Portion at Fair Value, Fair Value Disclosure | Fair Value, Inputs, Level 1
Financial assets:
Cash and due from banks	2,235
Other short-term investments	1,628
Financial liabilities:
Deposits	0
Federal funds purchased	319
Long-term debt	8,305
Portion at Fair Value, Fair Value Disclosure | Fair Value, Inputs, Level 2
Financial assets:
Other securities	842
Financial liabilities:
Deposits	85,912
Other short-term borrowings	2,877
Long-term debt	1,861
Portion at Fair Value, Fair Value Disclosure | Fair Value, Inputs, Level 3
Financial assets:
Held-to-maturity securities	321
Loans held for sale	155
Portfolio loans and leases:
Commercial and industrial loans	32,075
Commercial mortgage loans	8,697
Commercial construction loans	689
Commercial leases	3,203
Residential mortgage loans	10,627
Home equity	9,866
Automobile loans	11,755
Credit card	1,903
Other consumer loans and leases	319
Total portfolio loans and leases, net	$ 79,134

[1] Includes $19, $30 and $54 of cash, $4, $7 and $7of other short-term investments, $50, $50 and $29 of commercial mortgage loans, $217, $223 and $236 of home equity loans, $105, $259 and $529 of automobile loans, ($7), ($10) and ($12) of ALLL, $3, $4 and $5 of other assets, $3, $4 and $10 of other liabilities, $125, $191and $492 of long-term debt from consolidated VIEs that are included in their respective captions above at March 31, 2012, December 31, 2011 and March 31, 2011, respectively. See Note 8.

[2] Includes $67, $65 and $54 of residential mortgage loans measured at fair value at March 31, 2012, December 31, 2011 and March 31, 2011, respectively.

[3] Excludes $67 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.