Employer Sponsored Benefit Plans - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Components of employer benefit cost
Service cost	$ 40	$ 30	$ 120	$ 90
Interest cost	428	530	1,285	2,356
Expected return on assets	(532)	(488)	(1,597)	(2,105)
Amortization of actuarial loss	0	0	2	464
Net periodic benefit cost	(64)	72	(190)	805
Settlement loss	0	186	385	25,701
Total employer benefit plan cost	$ (64)	$ 258	$ 195	$ 26,506