Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
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	8	$ 11
Interest cost	315	326
Expected return on plan assets	(752)	(687)
Amortization of net loss (gain)	0	17
Amortization of prior service (credit) cost	0	0
Net periodic benefit	(429)	(333)
Other Postretirement Benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost	18	26
Interest cost	60	54
Expected return on plan assets	(248)	(190)
Amortization of net loss (gain)	(48)	(89)
Amortization of prior service (credit) cost	(85)	23
Net periodic benefit	$ (303)	$ (176)