Retirement Plans - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Employee service period under ESOP	1 year
Deferred compensation obligations	$ 6,043	$ 7,923
Cash values of the insurance policies purchased to fund deferred compensation obligations	118,870	117,823	$ 117,318
Unfunded status of the supplemental retirement plans	1,294	11,193
Deferred tax asset		3,309
Net actuarial loss	$ (254)
401(k) Plan
Defined Benefit Plan Disclosure [Line Items]
Minimum age for employees	21 years
Minimum period for employees to participate	90 days
Discretionary matching contribution equal to percentage of participant's contribution	50.00%
Discretionary matching contribution maximum percentage of eligible compensation	4.00%
Supplemental Retirement Plans
Defined Benefit Plan Disclosure [Line Items]
Cash values of the insurance policies purchased to fund deferred compensation obligations	$ 118,870	117,823
Unfunded status of the supplemental retirement plans	(1,294)	(11,193)
Accumulated other comprehensive loss	(912)	$ (7,884)
Deferred tax asset	$ 382