Securities Available-for-Sale - Summary of Securities Available-for-Sale (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 345,709	$ 336,751
Gross Unrealized Gains	329	635
Gross Unrealized Losses	949	627
Total, Fair Value	345,089	336,759
U.S. Treasury [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,000	2,000
Gross Unrealized Losses	2	8
Total, Fair Value	1,998	1,992
U.S. Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,950	3,946
Gross Unrealized Losses	8	31
Total, Fair Value	3,942	3,915
SBA Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	72,906	70,477
Gross Unrealized Gains		1
Gross Unrealized Losses	318	284
Total, Fair Value	72,588	70,194
U.S. Government Agency and Sponsored Enterprises Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	194,549	162,604
Gross Unrealized Gains	228	536
Gross Unrealized Losses	572	250
Total, Fair Value	194,205	162,890
Privately Issued Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	653	679
Gross Unrealized Gains	4	3
Gross Unrealized Losses	8	10
Total, Fair Value	649	672
Obligations Issued by States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	68,051	93,445
Gross Unrealized Gains	56	58
Total, Fair Value	68,107	93,503
Other Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,600	3,600
Gross Unrealized Gains	41	37
Gross Unrealized Losses	41	44
Total, Fair Value	$ 3,600	$ 3,593