Loans and Allowance for Credit Losses - Schedule of Average Balance and Interest Income Recognized on Impaired Loans (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment, Total	$ 78,868	$ 71,721	$ 76,390	$ 72,039
Interest Income Recognized	74	112	197	168
Commercial Loan [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment with no related allowance	10,294	7,525	9,605	8,393
Interest Income Recognized with no related allowance	58	(4)	58
Average Recorded Investment with an allowance recorded	17,815	20,831	19,945	21,365
Interest Income Recognized with an allowance recorded	21	39	31	68
Commercial Real Estate Construction Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment with no related allowance	854	987	891	1,136
Interest Income Recognized with no related allowance
Average Recorded Investment with an allowance recorded	2,684	1,593	3,036	1,532
Interest Income Recognized with an allowance recorded				2
Commercial Real Estate Other Receivable [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment with no related allowance	14,865	14,241	15,212	15,730
Interest Income Recognized with no related allowance	9	33	13	43
Average Recorded Investment with an allowance recorded	32,356	26,544	27,701	23,883
Interest Income Recognized with an allowance recorded	$ (14)	$ 44	$ 95	$ 55

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 15

-Subparagraph (c)(1)

-URI http://asc.fasb.org/extlink&oid=28368275&loc=d3e5212-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 17

-URI http://asc.fasb.org/extlink&oid=28368275&loc=d3e5258-111524

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- Definition

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.

+ References

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- Definition

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

+ References

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- Definition

Amount of interest income, recognized on accrual basis, on financing receivables that are recognized as impaired, for which there is no related allowance for credit losses.

+ References

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

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- Definition

Amount of interest income, recognized on accrual basis, on financing receivables, for which there is a related allowance for credit losses and are recognized as impaired.

+ References

+ Details

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