Loans Receivable and Allowance for Loan Losses - Summary of Impaired Loans (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Impaired [Line Items]
Recorded Investment Net of Charge Offs, Total	$ 40,325	$ 39,280
Unpaid Principle Balance, Total	44,234	43,639
Related Allowance	1,342	2,342
Average Recorded Investment, Total	40,709	56,539
Interest Income Recognized, Total	1,684	1,681
Commercial and industrial
Financing Receivable, Impaired [Line Items]
Recorded Investment Net of Charge Offs, With no related allowance recorded	13,825	13,097
Unpaid Principal Balance, With no related allowance recorded	15,348	13,159
With no related allowance recorded, Average Recorded Investment	13,329	9,953
With no related allowance recorded, Interest Income Recognized	674	603
Recorded Investment Net of Charge Offs, With an allowance recorded	1,833	2,469
Unpaid Principal Balance, With an allowance recorded	1,833	3,739
Related Allowance	818	829
With an allowance recorded, Average Recorded Investment	1,725	1,616
With an allowance recorded, Interest Income Recognized	28	44
Commercial real estate
Financing Receivable, Impaired [Line Items]
Recorded Investment Net of Charge Offs, With no related allowance recorded	18,977	14,397
Unpaid Principal Balance, With no related allowance recorded	19,121	15,249
With no related allowance recorded, Average Recorded Investment	17,974	22,475
With no related allowance recorded, Interest Income Recognized	887	978
Recorded Investment Net of Charge Offs, With an allowance recorded	1,410	2,261
Unpaid Principal Balance, With an allowance recorded	1,410	3,167
Related Allowance	304	946
With an allowance recorded, Average Recorded Investment	2,086	7,497
With an allowance recorded, Interest Income Recognized	39	2
Construction
Financing Receivable, Impaired [Line Items]
Recorded Investment Net of Charge Offs, With no related allowance recorded	2,325	2,777
Unpaid Principal Balance, With no related allowance recorded	2,325	4,046
With no related allowance recorded, Average Recorded Investment	2,415	6,408
With no related allowance recorded, Interest Income Recognized	41	6
Recorded Investment Net of Charge Offs, With an allowance recorded	0	1,132
Unpaid Principal Balance, With an allowance recorded	0	1,132
Related Allowance	0	351
With an allowance recorded, Average Recorded Investment	851	5,054
With an allowance recorded, Interest Income Recognized	0	0
Home equity / other
Financing Receivable, Impaired [Line Items]
Recorded Investment Net of Charge Offs, With no related allowance recorded	21	0
Unpaid Principal Balance, With no related allowance recorded	21	0
With no related allowance recorded, Average Recorded Investment	26	90
With no related allowance recorded, Interest Income Recognized	0	8
Recorded Investment Net of Charge Offs, With an allowance recorded	114	64
Unpaid Principal Balance, With an allowance recorded	114	64
Related Allowance	32	17
With an allowance recorded, Average Recorded Investment	82	48
With an allowance recorded, Interest Income Recognized	1	5
Residential Real Estate
Financing Receivable, Impaired [Line Items]
Recorded Investment Net of Charge Offs, With no related allowance recorded	1,455	2,831
Unpaid Principal Balance, With no related allowance recorded	3,697	2,831
With no related allowance recorded, Average Recorded Investment	1,925	2,523
With no related allowance recorded, Interest Income Recognized	13	31
Recorded Investment Net of Charge Offs, With an allowance recorded	365	252
Unpaid Principal Balance, With an allowance recorded	365	252
Related Allowance	188	199
With an allowance recorded, Average Recorded Investment	296	875
With an allowance recorded, Interest Income Recognized	$ 1	$ 4

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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=35738203&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=35738203&loc=d3e5258-111524

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+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 14A

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-URI http://asc.fasb.org/extlink&oid=35738203&loc=SL6953550-111524

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