Employee Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Pension Benefits
Components of the net periodic benefit cost
Interest cost	$ 29	$ 33
Recognized net actuarial loss	58	61
Benefit cost (income)	87	94
Postretirement Benefits
Components of the net periodic benefit cost
Interest cost	206	187
Service cost	73	87
Amortization of prior service cost	(228)	(228)
Benefit cost (income)	$ 51	$ 46