Pension Plans and Other Postretirement Benefits (Components of Net Periodic (Benefit) Cost ) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Pension Benefits
Pension plans and other postretirement benefits
Interest cost	$ 2,455	$ 2,592	$ 4,965	$ 5,225
Expected return on plan assets	(3,634)	(3,709)	(7,267)	(7,422)
Recognized net actuarial loss (gain)	729	342	1,486	701
Amortization of prior service cost	48	48	95	95
Net periodic (benefit) cost	(402)	(727)	(721)	(1,401)
Other Postretirement Benefits
Pension plans and other postretirement benefits
Service cost	596	402	1,065	621
Interest cost	226	243	502	465
Recognized net actuarial loss (gain)	0	(93)	0	(244)
Net periodic (benefit) cost	$ 822	$ 552	$ 1,567	$ 842