Employer Sponsored Benefit Plans - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Components of net periodic benefit cost
Service cost	$ 30	$ 0
Interest cost	982	470
Expected return on assets	(872)	(650)
Amortization of actuarial loss	278	256
Net periodic benefit cost	$ 418	$ 76