Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 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	$ 16	$ 15	31	$ 30
Interest cost	349	330	686	660
Expected return on plan assets	(681)	(684)	(1,325)	(1,368)
Amortization of net (gain) loss	5	121	92	81
Amortization of prior service cost	0	0	0	0
Net periodic benefit	(311)	(218)	(516)	(597)
Other Postretirement Benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost	32	39	64	78
Interest cost	61	64	123	129
Expected return on plan assets	(180)	(180)	(360)	(361)
Amortization of net (gain) loss	(55)	(106)	(109)	(71)
Amortization of prior service cost	22	67	45	45
Net periodic benefit	$ (120)	$ (116)	$ (237)	$ (180)