Allowance for Loan Losses - Loans by Risk Rating (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Loans by risk rating
Financing Receivable, Net	$ 1,731,536	$ 1,331,366
Construction and Land Development [Member]
Loans by risk rating
Financing Receivable, Net	27,421	22,744
Construction and Land Development [Member] | 1-3 (Pass) [Member]
Loans by risk rating
Financing Receivable, Net	20,281	15,515
Construction and Land Development [Member] | 4 (Monitor) [Member]
Loans by risk rating
Financing Receivable, Net	7,042	7,126
Construction and Land Development [Member] | Impaired [Member]
Loans by risk rating
Financing Receivable, Net	98	103
Commercial and Industrial [Member]
Loans by risk rating
Financing Receivable, Net	452,235	149,732
Commercial and Industrial [Member] | 1-3 (Pass) [Member]
Loans by risk rating
Financing Receivable, Net	451,774	148,407
Commercial and Industrial [Member] | 4 (Monitor) [Member]
Loans by risk rating
Financing Receivable, Net	18	472
Commercial and Industrial [Member] | Impaired [Member]
Loans by risk rating
Financing Receivable, Net	443	853
Municipal [Member]
Loans by risk rating
Financing Receivable, Net	85,685	41,850
Municipal [Member] | 1-3 (Pass) [Member]
Loans by risk rating
Financing Receivable, Net	85,685	41,850
Commercial Real Estate [Member]
Loans by risk rating
Financing Receivable, Net	721,506	696,272
Commercial Real Estate [Member] | 1-3 (Pass) [Member]
Loans by risk rating
Financing Receivable, Net	718,911	691,322
Commercial Real Estate [Member] | 4 (Monitor) [Member]
Loans by risk rating
Financing Receivable, Net	917	633
Commercial Real Estate [Member] | Impaired [Member]
Loans by risk rating
Financing Receivable, Net	$ 1,678	$ 4,317