Fair Value Disclosures - Assets, Liabilities and Off-balance Sheet Items Not Measured at Fair Value (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Assets:
Held-to-maturity securities	$ 41,061	$ 54,765
Deposits:
Time deposits	454,406	252,593
Subordinated notes	49,377	0
Fair Value [Member]
Assets:
Cash and short-term interest-earning assets	60,799	38,565
Held-to-maturity securities	41,061	54,765
Loans held for sale	4,708	3,374
Net loans and leases held for investment	2,099,082	1,555,033
Mortgage servicing rights	8,047	6,941
Other real estate owned	1,276	955
Total assets	2,214,973	1,659,633
Deposits:
Demand and savings deposits, non-maturity	1,939,954	1,608,748
Time deposits	455,527	254,224
Total deposits	2,395,481	1,862,972
Short-term borrowings	22,302	38,631
Subordinated notes	50,375
Total liabilities	2,468,158	1,901,603
Off-Balance-Sheet:
Commitments to extend credit	(1,788)	(1,420)
Fair Value [Member] | Level 1 [Member]
Assets:
Cash and short-term interest-earning assets	60,799	38,565
Held-to-maturity securities	0	0
Loans held for sale	0	0
Net loans and leases held for investment	0	0
Mortgage servicing rights	0	0
Other real estate owned	0	0
Total assets	60,799	38,565
Deposits:
Demand and savings deposits, non-maturity	1,939,954	1,608,748
Time deposits	0	0
Total deposits	1,939,954	1,608,748
Short-term borrowings	0	0
Subordinated notes	0
Total liabilities	1,939,954	1,608,748
Off-Balance-Sheet:
Commitments to extend credit	0	0
Fair Value [Member] | Level 2 [Member]
Assets:
Cash and short-term interest-earning assets	0	0
Held-to-maturity securities	41,061	54,765
Loans held for sale	4,708	3,374
Net loans and leases held for investment	0	0
Mortgage servicing rights	0	0
Other real estate owned	1,276	955
Total assets	47,045	59,094
Deposits:
Demand and savings deposits, non-maturity	0	0
Time deposits	455,527	254,224
Total deposits	455,527	254,224
Short-term borrowings	22,302	38,631
Subordinated notes	50,375
Total liabilities	528,204	292,855
Off-Balance-Sheet:
Commitments to extend credit	(1,788)	(1,420)
Fair Value [Member] | Level 3 [Member]
Assets:
Cash and short-term interest-earning assets	0	0
Held-to-maturity securities	0	0
Loans held for sale	0	0
Net loans and leases held for investment	2,099,082	1,555,033
Mortgage servicing rights	8,047	6,941
Other real estate owned	0	0
Total assets	2,107,129	1,561,974
Deposits:
Demand and savings deposits, non-maturity	0	0
Time deposits	0	0
Total deposits	0	0
Short-term borrowings	0	0
Subordinated notes	0
Total liabilities	0	0
Off-Balance-Sheet:
Commitments to extend credit	0	0
Carrying Amount [Member]
Assets:
Cash and short-term interest-earning assets	60,799	38,565
Held-to-maturity securities	40,990	54,347
Loans held for sale	4,680	3,302
Net loans and leases held for investment	2,112,774	1,550,770
Mortgage servicing rights	5,877	5,509
Other real estate owned	1,276	955
Total assets	2,226,396	1,653,448
Deposits:
Demand and savings deposits, non-maturity	1,939,954	1,608,748
Time deposits	454,406	252,593
Total deposits	2,394,360	1,861,341
Short-term borrowings	24,211	41,974
Subordinated notes	49,377
Total liabilities	2,467,948	1,903,315
Off-Balance-Sheet:
Commitments to extend credit	$ 0	$ 0