Allowance for Loan Losses - Summary of Allowance for Loan Losses and Recorded Investments (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	$ 54	$ 97
Allowance for Loan Losses, Collectively Evaluated for Impairment	47,857	46,158
Total Allowance for Loan Losses	47,911	46,255	46,484
Portfolio Loans, Individually Evaluated for Impairment	43,977	52,856
Portfolio Loans, Collectively Evaluated for Impairment	3,824,769	3,513,343
Total Portfolio Loans	3,868,746	3,566,199
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	0	0
Allowance for Loan Losses, Collectively Evaluated for Impairment	20,164	18,921
Total Allowance for Loan Losses	20,164	18,921	25,246
Portfolio Loans, Individually Evaluated for Impairment	19,890	26,968
Portfolio Loans, Collectively Evaluated for Impairment	1,662,346	1,580,788
Total Portfolio Loans	1,682,236	1,607,756
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	0	0
Allowance for Loan Losses, Collectively Evaluated for Impairment	13,668	14,433
Total Allowance for Loan Losses	13,668	14,433	7,759
Portfolio Loans, Individually Evaluated for Impairment	9,218	9,580
Portfolio Loans, Collectively Evaluated for Impairment	984,920	832,869
Total Portfolio Loans	994,138	842,449
Commercial Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	0	25
Allowance for Loan Losses, Collectively Evaluated for Impairment	6,093	5,349
Total Allowance for Loan Losses	6,093	5,374	7,500
Portfolio Loans, Individually Evaluated for Impairment	7,605	8,072
Portfolio Loans, Collectively Evaluated for Impairment	208,543	135,603
Total Portfolio Loans	216,148	143,675
Consumer Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	43	53
Allowance for Loan Losses, Collectively Evaluated for Impairment	6,290	6,309
Total Allowance for Loan Losses	6,333	6,362	5,058
Portfolio Loans, Individually Evaluated for Impairment	7,202	8,079
Portfolio Loans, Collectively Evaluated for Impairment	903,455	896,357
Total Portfolio Loans	910,657	904,436
Other Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	11	19
Allowance for Loan Losses, Collectively Evaluated for Impairment	1,642	1,146
Total Allowance for Loan Losses	1,653	1,165	921
Portfolio Loans, Individually Evaluated for Impairment	62	157
Portfolio Loans, Collectively Evaluated for Impairment	65,505	67,726
Total Portfolio Loans	$ 65,567	$ 67,883

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

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

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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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The balance of financing receivables that were collectively evaluated for impairment.

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The balance of financing receivables that were individually evaluated for impairment.

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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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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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