Retirement Plans - Schedule of Net Benefit Costs (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Compensation And Retirement Disclosure [Abstract]
Interest cost	$ 251	$ 286	$ 753	$ 858
Net amortization	72	52	216	156
Net periodic pension cost	$ 323	$ 338	$ 969	$ 1,014