Securities - Reconciliation of Held-to-Maturity Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 90,766	$ 123,975
Gross Unrealized Gains	3,114	1,115
Gross Unrealized Losses	(12)	(186)
Allowance for Credit Losses	0	0
Fair Value	93,868	124,904
U.S. government agencies
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	25,565	31,335
Gross Unrealized Gains	779	182
Gross Unrealized Losses	0	(8)
Allowance for Credit Losses	0
Fair Value	26,344	31,509
Mortgage-backed securities, residential
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	39,276	48,082
Gross Unrealized Gains	1,469	562
Gross Unrealized Losses	(12)	(121)
Allowance for Credit Losses	0
Fair Value	40,733	48,523
Collateralized mortgage obligations, residential
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	14,590	28,147
Gross Unrealized Gains	532	172
Gross Unrealized Losses	0	(55)
Allowance for Credit Losses	0
Fair Value	15,122	28,264
Mortgage-backed securities, multifamily
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	705	1,750
Gross Unrealized Gains	54	4
Gross Unrealized Losses	0	(2)
Allowance for Credit Losses	0
Fair Value	759	1,752
Obligations of states and political subdivisions
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	10,630	12,161
Gross Unrealized Gains	280	195
Gross Unrealized Losses	0	0
Allowance for Credit Losses	0
Fair Value	$ 10,910	12,356
Debt securities
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost		2,500
Gross Unrealized Gains		0
Gross Unrealized Losses		0
Fair Value		$ 2,500