Allowance for Loan Losses - Summary of Allowance for Loan Losses (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Allowance for loan losses:
Allowance for loan losses, beginning of period	$ 23,075	$ 22,318
Charge-offs	(69)	(81)
Recoveries	88	92
Provision	450	200
Allowance for loan losses, end of period	23,544	22,529
Amount of allowance for loan losses for loans deemed to be impaired	229	929
Amount of allowance for loan losses for loans not deemed to be impaired	23,315	21,600
Loans:
Total loans, net	1,762,458	1,341,330	$ 1,731,536
Loans deemed to be impaired	3,186	6,321
Loans not deemed to be impaired	1,759,272	1,335,009
Construction and Land Development [Member]
Allowance for loan losses:
Allowance for loan losses, beginning of period	2,041	1,592
Provision	(68)	292
Allowance for loan losses, end of period	1,973	1,884
Amount of allowance for loan losses for loans deemed to be impaired	7	20
Amount of allowance for loan losses for loans not deemed to be impaired	1,966	1,864
Loans:
Total loans, net	26,572	25,347	27,421
Loans deemed to be impaired	98	102
Loans not deemed to be impaired	26,474	25,245
Commercial and Industrial [Member]
Allowance for loan losses:
Allowance for loan losses, beginning of period	5,899	4,758
Recoveries	35	15
Provision	759	(128)
Allowance for loan losses, end of period	6,693	4,645
Amount of allowance for loan losses for loans deemed to be impaired	17	96
Amount of allowance for loan losses for loans not deemed to be impaired	6,676	4,549
Loans:
Total loans, net	529,168	157,637	452,235
Loans deemed to be impaired	429	871
Loans not deemed to be impaired	528,739	156,766
Municipal [Member]
Allowance for loan losses:
Allowance for loan losses, beginning of period	994	1,488
Provision	(4)	(115)
Allowance for loan losses, end of period	990	1,373
Amount of allowance for loan losses for loans not deemed to be impaired	990	1,373
Loans:
Total loans, net	85,227	41,406	85,685
Loans not deemed to be impaired	85,227	41,406
Commercial Real Estate [Member]
Allowance for loan losses:
Allowance for loan losses, beginning of period	10,589	11,199
Recoveries		2
Provision	(56)	(74)
Allowance for loan losses, end of period	10,533	11,127
Amount of allowance for loan losses for loans deemed to be impaired	89	631
Amount of allowance for loan losses for loans not deemed to be impaired	10,444	10,496
Loans:
Total loans, net	715,248	691,811	721,506
Loans deemed to be impaired	1,665	4,304
Loans not deemed to be impaired	713,583	687,507
Residential Real Estate [Member]
Allowance for loan losses:
Allowance for loan losses, beginning of period	1,320	775
Recoveries	2	2
Provision	(73)	22
Allowance for loan losses, end of period	1,249	799
Amount of allowance for loan losses for loans deemed to be impaired	27	90
Amount of allowance for loan losses for loans not deemed to be impaired	1,222	709
Loans:
Total loans, net	215,040	258,558	255,346
Loans deemed to be impaired	905	952
Loans not deemed to be impaired	214,135	257,606
Consumer [Member]
Allowance for loan losses:
Allowance for loan losses, beginning of period	644	810
Charge-offs	(69)	(81)
Recoveries	51	73
Provision	67	(88)
Allowance for loan losses, end of period	693	714
Amount of allowance for loan losses for loans not deemed to be impaired	693	714
Loans:
Total loans, net	12,826	10,508	11,323
Loans not deemed to be impaired	12,826	10,508
Home Equity [Member]
Allowance for loan losses:
Allowance for loan losses, beginning of period	1,077	599
Provision	108	15
Allowance for loan losses, end of period	1,185	614
Amount of allowance for loan losses for loans deemed to be impaired	89	92
Amount of allowance for loan losses for loans not deemed to be impaired	1,096	522
Loans:
Total loans, net	178,377	156,063	$ 178,020
Loans deemed to be impaired	89	92
Loans not deemed to be impaired	178,288	155,971
Unallocated [Member]
Allowance for loan losses:
Allowance for loan losses, beginning of period	511	1,097
Provision	(283)	276
Allowance for loan losses, end of period	228	1,373
Amount of allowance for loan losses for loans not deemed to be impaired	$ 228	$ 1,373

Amount of allowance for loans losses for loans not deemed to be impaired.

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Provision for loan losses gains expensed.

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Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

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The recorded amount of loans and debt securities, with evidence of deterioration of credit quality since origination that were acquired by completion of a transfer for which it was probable, at acquisition, that the investor would be unable to collect all contractually required payments receivable, but which are not deemed to be impaired since the acquisition by transfer. Therefore, no allowance for credit losses is recorded.

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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 allowance for credit losses related to recorded investment.

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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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