Pension plan and 401(k) Program - Net Periodic Costs (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Retirement Benefits [Abstract]
Service cost	$ 836	$ 632
Interest cost	23	61
Expected return on plan assets	(171)	(175)
Amortization of:
Prior service (benefit)	(5)	(5)
Net actuarial loss	146	49
Participant contributions	(213)	(194)
Net periodic benefit cost	$ 616	$ 368