Securities Available-for-Sale - Summary of Securities Available-for-Sale (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 336,751	$ 395,947
Gross Unrealized Gains	635	673
Gross Unrealized Losses	627	790
Total, Fair Value	336,759	395,830
U.S. Treasury [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,000	1,999
Gross Unrealized Losses	8	15
Total, Fair Value	1,992	1,984
U.S. Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,946
Gross Unrealized Losses	31
Total, Fair Value	3,915
SBA Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	70,477	81,065
Gross Unrealized Gains	1	46
Gross Unrealized Losses	284	161
Total, Fair Value	70,194	80,950
U.S. Government Agency and Sponsored Enterprises Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	162,604	225,537
Gross Unrealized Gains	536	555
Gross Unrealized Losses	250	317
Total, Fair Value	162,890	225,775
Privately Issued Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	679	897
Gross Unrealized Gains	3	4
Gross Unrealized Losses	10	9
Total, Fair Value	672	892
Obligations Issued by States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	93,445	82,849
Gross Unrealized Gains	58
Gross Unrealized Losses		249
Total, Fair Value	93,503	82,600
Other Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,600	3,600
Gross Unrealized Gains	37	68
Gross Unrealized Losses	44	39
Total, Fair Value	$ 3,593	$ 3,629