Carrying Amounts and Estimated Fair Values for Certain Financial Instruments (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013		Dec. 31, 2012		Jun. 30, 2012	Dec. 31, 2011
Financial assets:
Cash and due from banks	$ 2,390		$ 2,441		$ 2,393	$ 2,663
Held-to-maturity securities	274		284
Other short-term investments	1,109		2,421
Loans held for sale	2,113		2,856
Portfolio loans and leases:
Commercial and industrial loans	37,856		36,038
Commercial mortgage loans	8,443	[1]	9,103	[1]
Commercial construction loans	754		698
Commercial leases	3,567		3,549
Residential mortgage loans	12,400	[2]	12,017	[2]
Home equity	9,531		10,018
Automobile loans	12,015		11,972
Credit card	2,114		2,097
Other consumer loans and leases	352		290
Financial liabilities:
Federal funds purchased	636		901
Fair Value, Inputs, Level 2
Financial assets:
Loans held for sale	2,113	[3]	2,856	[3]
Carrying (Reported) Amount, Fair Value Disclosure
Financial assets:
Cash and due from banks	2,390		2,441
Other securities	845		844
Held-to-maturity securities	274		284
Other short-term investments	1,109		2,421
Loans held for sale	35		83
Portfolio loans and leases:
Commercial and industrial loans	37,039		35,236
Commercial mortgage loans	8,165		8,770
Commercial construction loans	727		665
Commercial leases	3,506		3,481
Residential mortgage loans	12,116	[4]	11,712	[5]
Home equity	9,411		9,875
Automobile loans	11,989		11,944
Credit card	2,031		2,010
Other consumer loans and leases	334		270
Unallocated allowance for loan and lease losses	(104)		(111)
Total portfolio loans and leases, net	85,214	[4]	83,852	[5]
Financial liabilities:
Deposits	93,454		89,517
Federal funds purchased	636		901
Other short-term borrowings	2,112		6,280
Long-term debt	6,940		7,085
Portion at Fair Value, Fair Value Disclosure
Financial assets:
Cash and due from banks	2,390		2,441
Other securities	845		844
Held-to-maturity securities	274		284
Other short-term investments	1,109		2,421
Loans held for sale	35		83
Portfolio loans and leases:
Commercial and industrial loans	38,882		36,496
Commercial mortgage loans	7,680		8,020
Commercial construction loans	608		505
Commercial leases	3,279		3,310
Residential mortgage loans	11,427	[4]	11,532	[5]
Home equity	9,340		9,798
Automobile loans	11,819		12,076
Credit card	2,172		2,139
Other consumer loans and leases	348		288
Total portfolio loans and leases, net	85,555	[4]	84,164	[5]
Financial liabilities:
Deposits	93,503		89,592
Federal funds purchased	636		901
Other short-term borrowings	2,112		6,280
Long-term debt	7,390		7,809
Portion at Fair Value, Fair Value Disclosure | Fair Value, Inputs, Level 1
Financial assets:
Cash and due from banks	2,390		2,441
Other short-term investments	1,109		2,421
Financial liabilities:
Federal funds purchased	636		901
Long-term debt	6,710		6,925
Portion at Fair Value, Fair Value Disclosure | Fair Value, Inputs, Level 2
Financial assets:
Other securities	845		844
Financial liabilities:
Deposits	93,503		89,592
Other short-term borrowings	2,112		6,280
Long-term debt	680		884
Portion at Fair Value, Fair Value Disclosure | Fair Value, Inputs, Level 3
Financial assets:
Held-to-maturity securities	274		284
Loans held for sale	35		83
Portfolio loans and leases:
Commercial and industrial loans	38,882		36,496
Commercial mortgage loans	7,680		8,020
Commercial construction loans	608		505
Commercial leases	3,279		3,310
Residential mortgage loans	11,427	[4]	11,532	[5]
Home equity	9,340		9,798
Automobile loans	11,819		12,076
Credit card	2,172		2,139
Other consumer loans and leases	348		288
Total portfolio loans and leases, net	$ 85,555	[4]	$ 84,164	[5]

[1] Includes $50 and $50 of commercial mortgage loans, $(13) and $(5) of ALLL, and $1 and $3 of other assets from consolidated VIEs that are included in their respective captions above at June 30, 2013 and December 31, 2012, respectively. See Note 8.

[2] Includes $83 and $76 of residential mortgage loans measured at fair value at June 30, 2013 and December 31, 2012, respectively.

[3] During the three and six months ended June 30, 2013 and for the year ended December 31, 2012, no assets or liabilities were transferred between Level 1 and Level 2.

[4] Excludes $83 of residential mortgage loans measured at fair value on a recurring basis.

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