Pension Benefits (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Net periodic benefit cost:
Service cost	$ 325	$ 313	$ 975	$ 988
Interest cost	1,593	1,995	4,838	5,999
Expected return on plan assets	(3,280)	(3,318)	(9,838)	(9,979)
Amortization of net actuarial loss	235	205	750	589
Total net periodic benefit	$ (1,127)	$ (805)	$ (3,275)	$ (2,403)
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	$ 6,000