Securities - Securities Available for Sale in Unrealized Loss Position (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Schedule of Available-for-sale Securities [Line Items]
Fair value, Less than 12 months	$ 11,275	$ 14,950
Unrealized loss, Less than 12 months	(27)	(53)
Fair value, 12 months or more	85,674	193,973
Unrealized loss, 12 months or more	(821)	(5,007)
Total Fair value	96,949	208,923
Total, unrealized loss	(848)	(5,060)
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair value, Less than 12 months	1,716
Unrealized loss, Less than 12 months	(1)
Total Fair value	1,716
Total, unrealized loss	(1)
Mortgage-Backed Securities (MBS) [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair value, Less than 12 months	9,559
Unrealized loss, Less than 12 months	(26)
Fair value, 12 months or more	85,674	73,542
Unrealized loss, 12 months or more	(821)	(2,314)
Total Fair value	95,233	73,542
Total, unrealized loss	$ (847)	(2,314)
U.S. Treasury and Agency Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair value, 12 months or more		95,581
Unrealized loss, 12 months or more		(2,204)
Total Fair value		95,581
Total, unrealized loss		(2,204)
States and Municipalities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair value, Less than 12 months		9,475
Unrealized loss, Less than 12 months		(39)
Fair value, 12 months or more		24,850
Unrealized loss, 12 months or more		(489)
Total Fair value		34,325
Total, unrealized loss		(528)
Collateralized Mortgage Obligations (CMO) [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair value, Less than 12 months		5,475
Unrealized loss, Less than 12 months		(14)
Total Fair value		5,475
Total, unrealized loss		$ (14)