Securities Available-for-Sale - Summary of Securities Available-for-Sale (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 411,709	$ 500,220
Gross Unrealized Gains	780	555
Gross Unrealized Losses	1,149	1,478
Total, Fair Value	411,340	499,297
U.S. Treasury [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,999	2,000
Gross Unrealized Losses	4
Total, Fair Value	1,995	2,000
U.S. Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	10,000	25,000
Gross Unrealized Losses		48
Total, Fair Value	10,000	24,952
SBA Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	71,357	57,899
Gross Unrealized Gains	27	14
Gross Unrealized Losses	195	146
Total, Fair Value	71,189	57,767
U.S. Government Agency and Sponsored Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	223,655	243,703
Gross Unrealized Gains	463	293
Gross Unrealized Losses	336	671
Total, Fair Value	223,782	243,325
Privately Issued Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,025	1,121
Gross Unrealized Gains	3	2
Gross Unrealized Losses	13	14
Total, Fair Value	1,015	1,109
Obligations Issued by States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	98,457	165,281
Gross Unrealized Losses	408	405
Total, Fair Value	98,049	164,876
Other Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	5,100	5,100
Gross Unrealized Gains	85	18
Gross Unrealized Losses	193	194
Total, Fair Value	4,992	4,924
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	116	116
Gross Unrealized Gains	202	228
Total, Fair Value	$ 318	$ 344