Asset Quality - Concession Types for our Commercial Accruing and Nonaccruing TDRs (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Interest rate reduction	$ 104	$ 177
Forgiveness of principal	7	23
Other modification of loan terms	7	8
Total	118	208
Total commercial and consumer TDRs	320	276
Total commercial TDRs to total commercial loans	0.32%	0.60%
Total commercial TDRs to total loans	0.22%	0.42%
Total commercial loans	36,880	34,782
Total loans	$ 52,822	$ 49,575

Amount before allowance of commercial loans and leases receivable includes, but not limited to, commercial and industrial loans, agricultural loans, mortgage loans, promissory notes, interbank and other loans to financial institutions, draws against credit facilities, trade financing, lease financings. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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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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