Employer Sponsored Benefit Plans - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Components of employer benefit cost
Service cost	$ 40	$ 30	$ 80	$ 60
Interest cost	428	833	857	1,827
Expected return on assets	(532)	(744)	(1,065)	(1,616)
Amortization of actuarial loss	0	186	2	464
Net periodic benefit cost	(64)	305	(126)	735
Settlement loss	0	25,515	385	25,515
Total employer benefit plan cost	$ (64)	$ 25,820	$ 259	$ 26,250