Investment Securities - Reconciliation of Held-to-Maturity Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 160,328	$ 153,646
Gross Unrealized Gains	1,135	282
Gross Unrealized Losses	(435)	(2,996)
Investment securities held to maturity, Fair Value	161,028	150,932
U.S. government agencies
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	32,123	33,025
Gross Unrealized Gains	152	0
Gross Unrealized Losses	(65)	(677)
Investment securities held to maturity, Fair Value	32,210	32,348
Mortgage-backed securities, residential
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	86,392	75,859
Gross Unrealized Gains	531	169
Gross Unrealized Losses	(314)	(1,838)
Investment securities held to maturity, Fair Value	86,609	74,190
Mortgage-backed securities, multifamily
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	1,800	1,853
Gross Unrealized Gains	5	0
Gross Unrealized Losses	(9)	(35)
Investment securities held to maturity, Fair Value	1,796	1,818
Obligations of states and political subdivisions
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	33,513	37,909
Gross Unrealized Gains	443	113
Gross Unrealized Losses	(47)	(328)
Investment securities held to maturity, Fair Value	33,909	37,694
Debt securities
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	6,500	5,000
Gross Unrealized Gains	4	0
Gross Unrealized Losses	0	(118)
Investment securities held to maturity, Fair Value	$ 6,504	$ 4,882