Investment Securities - Reconciliation of Held-to-Maturity Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 109,834	$ 123,975
Gross Unrealized Gains	3,411	1,115
Gross Unrealized Losses	(4)	(186)
Fair Value	113,241	124,904
U.S. government agencies
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	30,926	31,335
Gross Unrealized Gains	929	182
Gross Unrealized Losses	(2)	(8)
Fair Value	31,853	31,509
Mortgage-backed securities, residential
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	65,470	76,229
Gross Unrealized Gains	2,147	734
Gross Unrealized Losses	(2)	(176)
Fair Value	67,615	76,787
Mortgage-backed securities, multifamily
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	728	1,750
Gross Unrealized Gains	51	4
Gross Unrealized Losses	0	(2)
Fair Value	779	1,752
Obligations of states and political subdivisions
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	10,210	12,161
Gross Unrealized Gains	284	195
Gross Unrealized Losses	0	0
Fair Value	10,494	12,356
Debt securities
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	2,500	2,500
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	$ 2,500	$ 2,500