Components of Net Periodic Benefit Cost (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Service cost	$ 31	$ 26	$ 50
Interest cost	37	54	62
Expected return on plan assets	(15)	(16)	(18)
Curtailments	0	95	0
Defined Benefit Plan, Plan Assets, Payment for Settlement	21	0	0
Amortization of prior service cost	36	67	69
Amortization of plan loss	38	17	20
Net periodic pension benefit cost	$ 148	$ 243	$ 183