Employee Benefit Plans - Components of Net Periodic Pension Cost for Defined Benefit Pension Plan and Retirement Plan (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Retirement Benefits [Abstract]
Service cost	$ 622	$ 503	$ 601
Interest cost	1,209	1,388	1,268
Expected return on plan assets	(1,761)	(1,644)	(1,784)
Amortization of actuarial losses	993	885	743
Net periodic pension cost	$ 1,063	$ 1,132	$ 828