Loans and Allowance for Loan Losses - Summary of Loans (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Receivables [Abstract]
Commercial and industrial	$ 21,433	$ 20,827
Commercial mortgage	9,918	9,939
Construction	659	627
Lease financing	1,060	1,104
Total commercial portfolio	33,070	32,497
Residential mortgage	23,146	22,705
Home equity and other consumer loans	3,542	3,647
Total consumer portfolio	26,688	26,352
Total loans held for investment, before purchased credit-impaired loans	59,758	58,849
Purchased credit-impaired loans	1,124	1,185
Total loans held for investment	60,882	60,034
Allowance for loan losses	(638)	(653)
Loans held for investment, net	$ 60,244	$ 59,381

Loans and Leases Receivable Allowance Including Credit Impaired Loans

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Loans and leases receivable, home equity and other consumer loans.

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Loans and leases receivable residential mortgages.

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Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes loans and leases covered under loss sharing agreements and acquired purchased credit-impaired loans.

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Loans acquired in a transfer, including business combinations, where there is evidence of credit deterioration since origination and it is probable at the date of acquisition that the Company will not collect all contractually required principal and interest payments are accounted for under accounting guidance for purchased credit-impaired loans. This guidance provides that the excess of the cash flows initially expected to be collected over the fair value of the loans at the acquisition date (i.e., the accretable yield) is accreted into interest income over the estimated remaining life of the purchased credit-impaired loans using the effective yield method, provided that the timing and amount of future cash flows is reasonably estimable. Accordingly, such loans are not classified as nonaccrual and are considered to be accruing because their interest income relates to the accretable yield recognized under accounting for purchased credit-impaired loans and not to contractual interest payments. The difference between the contractually required payments and the cash flows expected to be collected at acquisition, considering the impact of prepayments, is referred to as the nonaccretable difference.

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Amount before allowance of commercial leases and leveraged lease transactions where the entity is long-term creditor. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes leases covered under loss sharing agreements.

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Reflects the net carrying amount of commercial loans and leases held in portfolio, after deducting deferred income, but before deducting the allowance for losses on commercial loans and leases.

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Reflects the net carrying amount of consumer loans and leases held in portfolio, after deducting deferred income, but before deducting the allowance for losses on consumer loans and leases.

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Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

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Net carrying amount of all categories of loans and leases held in portfolio, net of unearned income and the allowance for losses on loans and leases. Includes receivables covered through loss sharing agreements.

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Amount before allowance of loans issued to commercial and industrial institutions. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes real estate loans and loans covered under loss sharing agreements.

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Amount before allowance of commercial construction loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans covered under loss sharing agreements.

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Amount before allowance of mortgage loans on existing land or building. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans covered under loss sharing agreements.

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