Regulatory Matters - Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Total Capital (to Risk-Weighted Assets):
Total Capital (to Risk-Weighted Assets) Actual, Amount	$ 462,198	$ 334,757
Total Capital (to Risk-Weighted Assets) Actual, Ratio	12.44%	13.35%
Total Capital (to Risk-Weighted Assets) For Capital Adequacy, Amount	$ 297,284	$ 200,613
Total Capital (to Risk-Weighted Assets) For Capital Adequacy, Ratio	8.00%	8.00%
Total Capital (to Risk-Weighted Assets) To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 371,604	$ 250,766
Total Capital (to Risk-Weighted Assets) To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	10.00%	10.00%
Tier 1 Capital (to Risk-Weighted Assets):
Tier 1 Capital (to Risk-Weighted Assets) Actual, Amount	$ 349,942	$ 267,098
Tier 1 Capital (to Risk-Weighted Assets) Actual, Ratio	9.42%	10.65%
Tier 1 Capital (to Risk - Weighed Assets) For Capital Adequacy, Amount	$ 222,963	$ 150,460
Tier 1 Capital (to Risk - Weighted Assets) For Capital Adequacy, Ratio	6.00%	6.00%
Tier 1 Capital (to Risk-Weighted Assets) To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 297,284	$ 200,613
Tier 1 Capital (to Risk-Weighted Assets) To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	8.00%	8.00%
Tier 1 Common Capital (to Risk-Weighted Assets)
Tier One Common Risk Based Capital	$ 349,942	$ 267,098
Tier One Common Risk Based Capital To Risk Weighted Assets	9.42%	10.65%
Tier One Common Risk Based Capital Required For Capital Adequacy	$ 167,222	$ 112,845
Tier One Common Risk Based Capital Required For Capital Adequacy To Risk Weighted Assets	4.50%	4.50%
Tier One Common Risk Based Capital Required To Be Well Capitalized	$ 241,543	$ 162,998
Tier One Common Risk Based Capital Required To Be Well Capitalized To Risk Weighted Assets	6.50%	6.50%
Tier 1 Capital (to Average Assets):
Tier 1 Capital (to Average Assets) Actual, Amount	$ 349,942	$ 267,098
Tier 1 Capital (to Average Assets) Actual, Ratio	8.84%	9.69%
Tier 1 Capital (to Average Assets) For Capital Adequacy, Amount	$ 158,410	$ 110,227
Tier 1 Capital (to Average Assets) For Capital Adequacy, Ratio	4.00%	4.00%
Tier 1 Capital (to Average Assets) To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 198,013	$ 137,783
Tier 1 Capital (to Average Assets) To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	5.00%	5.00%
Bank [Member]
Total Capital (to Risk-Weighted Assets):
Total Capital (to Risk-Weighted Assets) Actual, Amount	$ 436,435	$ 300,527
Total Capital (to Risk-Weighted Assets) Actual, Ratio	11.85%	12.09%
Total Capital (to Risk-Weighted Assets) For Capital Adequacy, Amount	$ 294,679	$ 198,816
Total Capital (to Risk-Weighted Assets) For Capital Adequacy, Ratio	8.00%	8.00%
Total Capital (to Risk-Weighted Assets) To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 368,349	$ 248,521
Total Capital (to Risk-Weighted Assets) To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	10.00%	10.00%
Tier 1 Capital (to Risk-Weighted Assets):
Tier 1 Capital (to Risk-Weighted Assets) Actual, Amount	$ 418,266	$ 282,245
Tier 1 Capital (to Risk-Weighted Assets) Actual, Ratio	11.36%	11.36%
Tier 1 Capital (to Risk - Weighed Assets) For Capital Adequacy, Amount	$ 221,010	$ 149,112
Tier 1 Capital (to Risk - Weighted Assets) For Capital Adequacy, Ratio	6.00%	6.00%
Tier 1 Capital (to Risk-Weighted Assets) To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 294,679	$ 198,816
Tier 1 Capital (to Risk-Weighted Assets) To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	8.00%	8.00%
Tier 1 Common Capital (to Risk-Weighted Assets)
Tier One Common Risk Based Capital	$ 418,266	$ 282,245
Tier One Common Risk Based Capital To Risk Weighted Assets	11.36%	11.36%
Tier One Common Risk Based Capital Required For Capital Adequacy	$ 165,757	$ 111,834
Tier One Common Risk Based Capital Required For Capital Adequacy To Risk Weighted Assets	4.50%	4.50%
Tier One Common Risk Based Capital Required To Be Well Capitalized	$ 239,427	$ 161,538
Tier One Common Risk Based Capital Required To Be Well Capitalized To Risk Weighted Assets	6.50%	6.50%
Tier 1 Capital (to Average Assets):
Tier 1 Capital (to Average Assets) Actual, Amount	$ 418,266	$ 282,245
Tier 1 Capital (to Average Assets) Actual, Ratio	10.64%	10.31%
Tier 1 Capital (to Average Assets) For Capital Adequacy, Amount	$ 157,254	$ 109,480
Tier 1 Capital (to Average Assets) For Capital Adequacy, Ratio	4.00%	4.00%
Tier 1 Capital (to Average Assets) To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 196,567	$ 136,850
Tier 1 Capital (to Average Assets) To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	5.00%	5.00%