Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Components of net periodic benefit cost [Abstract]
Contribution made to pension and postretirement plans	$ 0
Pension Benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost	12	$ 8
Interest cost	266	315
Expected return on plan assets	(819)	(752)
Amortization of net gain	0	0
Amortization of prior service credit	0	0
Net periodic benefit	(541)	(429)
Other Postretirement Benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost	19	18
Interest cost	54	60
Expected return on plan assets	(296)	(248)
Amortization of net gain	(166)	(48)
Amortization of prior service credit	(49)	(85)
Net periodic benefit	$ (438)	$ (303)