Regulatory Matters - Schedule of Regulatory Capital Ratios Under the Basel III Regulatory Capital Framework (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital to Risk-Weighted Assets, Actual Ratio	18.45%	16.97%
Tier1 Capital to Risk-Weighted Assets, Actual Ratio	17.30%	15.90%
Common Equity Tier1 Capital to Risk-Weighted Assets, Actual Ratio	17.30%	15.90%
Leverage Ratio, Actual Ratio	10.71%	9.96%
Consolidated [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital to Risk-Weighted Assets, Actual Amount	$ 739,959	$ 672,920
Tier1 Capital to Risk-Weighted Assets, Actual Amount	693,584	630,413
Common Equity Tier1 Capital to Risk-Weighted Assets, Actual Amount	693,584	630,413
Leverage Ratio, Actual Amount	$ 693,584	$ 630,413
Total Capital to Risk-Weighted Assets, Actual Ratio	18.45%	16.97%
Tier1 Capital to Risk-Weighted Assets, Actual Ratio	17.30%	15.90%
Common Equity Tier1 Capital to Risk-Weighted Assets, Actual Ratio	17.30%	15.90%
Leverage Ratio, Actual Ratio	10.71%	9.96%
Consolidated [Member] | Minimum [Member] | Basel III Fully Phased-In [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital to Risk-Weighted Assets, Minimum Capital Required	$ 421,007	$ 418,068
Tier1 Capital to Risk-Weighted Assets, Minimum Capital Required	340,815	338,436
Common Equity Tier1 Capital to Risk-Weighted Assets, Minimum Capital Required	280,671	278,712
Leverage Ratio, Minimum Capital Required	$ 258,978	$ 256,368
Total Capital to Risk-Weighted Assets, Minimum Capital Required	10.50%	10.50%
Tier1 Capital to Risk-Weighted Assets, Minimum Capital Required	8.50%	8.50%
Common Equity Tier1 Capital to Risk-Weighted Assets, Minimum Capital Required, Ratio	7.00%	7.00%
Leverage Ratio, Minimum Capital Required, Ratio	4.00%	4.00%
Consolidated [Member] | Minimum [Member] | Basel III Phase-In [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital to Risk-Weighted Assets, Minimum Capital Required	$ 345,827	$ 318,528
Tier1 Capital to Risk-Weighted Assets, Minimum Capital Required	265,635	238,896
Common Equity Tier1 Capital to Risk-Weighted Assets, Minimum Capital Required	205,491	179,172
Leverage Ratio, Minimum Capital Required	$ 258,978	$ 256,368
Total Capital to Risk-Weighted Assets, Minimum Capital Required	8.625%	8.00%
Tier1 Capital to Risk-Weighted Assets, Minimum Capital Required	6.625%	6.00%
Common Equity Tier1 Capital to Risk-Weighted Assets, Minimum Capital Required, Ratio	5.125%	4.50%
Leverage Ratio, Minimum Capital Required, Ratio	4.00%	4.00%
Parent Company [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital to Risk-Weighted Assets, Actual Amount	$ 633,403	$ 570,910
Tier1 Capital to Risk-Weighted Assets, Actual Amount	587,028	528,403
Common Equity Tier1 Capital to Risk-Weighted Assets, Actual Amount	587,028	528,403
Leverage Ratio, Actual Amount	$ 587,028	$ 528,403
Total Capital to Risk-Weighted Assets, Actual Ratio	15.84%	14.37%
Tier1 Capital to Risk-Weighted Assets, Actual Ratio	14.68%	13.30%
Common Equity Tier1 Capital to Risk-Weighted Assets, Actual Ratio	14.68%	13.30%
Leverage Ratio, Actual Ratio	9.10%	8.37%
Parent Company [Member] | Minimum [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital to Risk-Weighted Assets, Required To Be Considered Well Capitalized , Ratio	10.00%	10.00%
Total Capital to Risk-Weighted Assets, Required To Be Considered Well Capitalized, Amount	$ 399,919	$ 397,235
Tier1 Capital to Risk-Weighted Assets, Required To Be Considered Well Capitalized , Ratio	8.00%	8.00%
Tier1 Capital to Risk-Weighted Assets, Required To Be Considered Well Capitalized, Amount	$ 319,935	$ 317,788
Common Equity Tier1 Capital to Risk-Weighted Assets, Required To Be Considered Well Capitalized , Ratio	6.50%	6.50%
Common Equity Tier1 Capital to Risk-Weighted Assets, Required To Be Considered Well Capitalized, Amount	$ 259,947	$ 258,203
Leverage Ratio, Required To Be Considered Well Capitalized , Ratio	5.00%	5.00%
Leverage Ratio, Required To Be Considered Well Capitalized, Amount	$ 322,426	$ 315,524
Parent Company [Member] | Minimum [Member] | Basel III Fully Phased-In [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital to Risk-Weighted Assets, Minimum Capital Required	419,915	417,097
Tier1 Capital to Risk-Weighted Assets, Minimum Capital Required	339,931	337,650
Common Equity Tier1 Capital to Risk-Weighted Assets, Minimum Capital Required	279,943	278,065
Leverage Ratio, Minimum Capital Required	$ 257,941	$ 252,419
Total Capital to Risk-Weighted Assets, Minimum Capital Required	10.50%	10.50%
Tier1 Capital to Risk-Weighted Assets, Minimum Capital Required	8.50%	8.50%
Common Equity Tier1 Capital to Risk-Weighted Assets, Minimum Capital Required, Ratio	7.00%	7.00%
Leverage Ratio, Minimum Capital Required, Ratio	4.00%	4.00%
Parent Company [Member] | Minimum [Member] | Basel III Phase-In [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital to Risk-Weighted Assets, Minimum Capital Required	$ 344,930	$ 317,788
Tier1 Capital to Risk-Weighted Assets, Minimum Capital Required	264,946	238,341
Common Equity Tier1 Capital to Risk-Weighted Assets, Minimum Capital Required	204,959	178,756
Leverage Ratio, Minimum Capital Required	$ 257,941	$ 252,419
Total Capital to Risk-Weighted Assets, Minimum Capital Required	8.625%	8.00%
Tier1 Capital to Risk-Weighted Assets, Minimum Capital Required	6.625%	6.00%
Common Equity Tier1 Capital to Risk-Weighted Assets, Minimum Capital Required, Ratio	5.125%	4.50%
Leverage Ratio, Minimum Capital Required, Ratio	4.00%	4.00%