Summary of Impaired Loans (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
Sep. 30, 2013	Dec. 31, 2012
Financing Receivable, Impaired [Line Items]
Impaired loans with a specific allowance	$ 15,142	$ 27,526
Impaired loans without a specific allowance	15,947	21,247
Total impaired loans	31,089	48,773
Allowance for loan and lease losses related to impaired loans	4,230	5,149
Allowance for loan and lease losses related to loans collectively evaluated	35,192	37,808
Total allowance for loan and lease losses	39,422	42,957
Average impaired loans for the period	39,843	57,438
Contractual interest income due on impaired loans during the period	2,292	4,433
Interest income on impaired loans recognized on a cash basis	1,694	1,121
Interest income on impaired loans recognized on an accrual basis	$ 332	$ 560

Loans and Leases Receivable, Impaired, Contractual Interest Income

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- Definition

The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

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Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

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Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

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Amount of interest income recognized that the financing receivables (with related allowance for credit losses and without a related allowance for credit losses) were impaired.

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Amount of interest income recognized on a cash-basis method of accounting that the financing receivables (with related allowance for credit losses and without a related allowance for credit losses) were impaired.

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Amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

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Amount of investment in impaired financing receivables for which there is no related allowance for credit losses.

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Amount of investment in impaired financing receivables for which there is a related allowance for credit losses.

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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