Income Taxes - Summary of Income Tax Provision Reconciled to Income Taxes that Computed at Statutory Federal Rate (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Federal income tax, at statutory rates	$ 15,703	$ 19,728	$ 16,861
Increase (deduction) in taxes resulting from:
Tax-exempt income	(961)	(952)	(1,096)
State income tax, net of federal income tax effect	2,178	4,322	1,880
Adjustment to net deferred tax asset for change in NJ tax law	0	0	(943)
Excess tax expense (benefits) from employee share-based payments	132	(189)	(318)
Other, net	207	363	504
Total provision for income taxes	$ 17,259	$ 23,272	$ 16,888