Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
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	$ 18	30	$ 36
Interest cost	330	336	660	672
Expected return on plan assets	(684)	(609)	(1,368)	(1,218)
Amortization of net loss (gain)	121	0	81	0
Amortization of prior service cost (credit)	0	0	0	0
Net periodic benefit	(218)	(255)	(597)	(510)
Other Postretirement Benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost	39	15	78	29
Interest cost	64	32	129	64
Expected return on plan assets	(180)	(169)	(361)	(338)
Amortization of net loss (gain)	(106)	(74)	(71)	(146)
Amortization of prior service cost (credit)	67	(45)	45	(90)
Net periodic benefit	$ (116)	$ (241)	$ (180)	$ (481)