Pension Plans and Other Postretirement Benefits (Components of Net Periodic (Benefit) Cost ) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Pension Benefits
Pension plans and other postretirement benefits
Interest cost	$ 2,482	$ 2,613	$ 7,447	$ 7,838
Expected return on plan assets	(3,634)	(3,710)	(10,901)	(11,132)
Recognized net actuarial loss (gain)	743	350	2,229	1,051
Amortization of prior service cost	48	47	143	142
Net periodic (benefit) cost	(361)	(700)	(1,082)	(2,101)
Other Postretirement Benefits
Pension plans and other postretirement benefits
Service cost	532	309	1,597	930
Interest cost	251	233	753	698
Recognized net actuarial loss (gain)	0	(122)	0	(366)
Net periodic (benefit) cost	$ 783	$ 420	$ 2,350	$ 1,262