Employee Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Pension Benefits
Components of the net periodic benefit cost
Interest cost	$ 29	$ 32	$ 58	$ 65
Recognized net actuarial loss	58	61	116	122
Benefit cost (income)	87	93	174	187
Postretirement Benefits
Components of the net periodic benefit cost
Interest cost	221	190	427	377
Service cost	64	75	138	162
Amortization of prior service cost	(228)	(228)	(456)	(456)
Benefit cost (income)	$ 57	$ 37	$ 109	$ 83