Employer Sponsored Benefit Plans - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Components of net periodic benefit cost
Service Cost	$ 12	$ 0	$ 12	$ 0
Interest cost	640	514	1,579	1,543
Expected return on assets	(893)	(594)	(2,193)	(1,782)
Amortization of actuarial loss	256	273	768	819
Net periodic benefit cost	$ 15	$ 193	$ 166	$ 580