Employer Sponsored Benefit Plans - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Components of employer benefit cost
Service cost	$ 30	$ 12	$ 90	$ 12
Interest cost	530	640	2,356	1,579
Expected return on assets	(488)	(893)	(2,105)	(2,193)
Amortization of actuarial loss	0	256	464	768
Net periodic benefit cost	72	15	805	166
Settlement loss	186	0	25,701	0
Total employer benefit plan cost	$ 258	$ 15	$ 26,506	$ 166