Retirement Plans - Schedule of Components of Net Periodic Benefit Cost (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Retirement Benefits [Abstract]
Service cost	$ 0	$ 0	$ 0
Interest cost on projected benefit obligation	23	34	38
Amortization of transition obligation	0	0	0
Gain amortization	(52)	(60)	(35)
Net periodic benefit cost	$ (29)	$ (26)	$ 3