Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
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	15	$ 15
Interest cost	337	330
Expected return on plan assets	(644)	(684)
Amortization of net (gain) loss	87	(40)
Amortization of prior service cost (credit)	0	0
Net periodic benefit	(205)	(379)
Other Postretirement Benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost	32	39
Interest cost	61	65
Expected return on plan assets	(181)	(181)
Amortization of net (gain) loss	(54)	35
Amortization of prior service cost (credit)	23	(22)
Net periodic benefit	$ (119)	$ (64)