Retirement Plans - Schedule of Changes in Benefit Obligations and Plan Assets (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Service cost	$ 0	$ 0	$ 0
Interest cost	23	34	38
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Funded Status at End of Year	1,372	834
Unrecognized transition obligation	(537)	0
Unrecognized net gain	308	463
Amounts recognized in retained earnings	1,143	1,297
Change in Benefit Obligation [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	834	883
Service cost	0	0
Interest cost	23	34
Amendments	537	0
Actuarial gain	102	61
Net benefits paid	(124)	(144)
Benefit obligation at end of year	1,372	834	883
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Net benefits paid	(124)	(144)
Change In Plan Assets [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Net benefits paid	(124)	(144)
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	0	0
Actual return on plan assets	0	0
Employer contributions	124	144
Net benefits paid	(124)	(144)
Fair value of plan assets at end of year	$ 0	$ 0	$ 0