Pension Benefits (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Net periodic benefit cost:
Service cost	$ 325	$ 337	$ 650	$ 675
Interest cost	1,622	2,002	3,245	4,004
Expected return on plan assets	(3,279)	(3,331)	(6,558)	(6,661)
Amortization of net actuarial loss	258	193	515	384
Total net periodic benefit	$ (1,074)	$ (799)	$ (2,148)	$ (1,598)
Weighted average assumptions used to determine net cost
Discount rate	3.00%	4.05%	3.00%	4.05%
Expected return on plan assets	6.50%	7.25%	6.50%	7.25%
Employer contributions			$ 1,500	$ 3,000