Pension and Other Postretirement Benefits (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Pensions [Member]
Pension and other postretirement benefits expenses
Service cost	$ 1,299	$ 1,052	$ 2,752	$ 2,307
Interest cost	5,297	5,540	9,992	10,978
Expected return on plan assets	(8,589)	(8,483)	(16,159)	(17,053)
Amortization of prior service cost (credit)	77	157	155	334
Amortization of actuarial losses	4,056	2,270	7,485	4,232
Curtailment loss	0	0	0	219
Settlement loss	0	582	0	582
Special termination benefits	0	0	0	715
Net periodic benefit cost	2,140	1,118	4,225	2,314
Other Postretirement Benefits [Member]
Pension and other postretirement benefits expenses
Service cost	36	29	73	81
Interest cost	425	540	918	1,099
Amortization of prior service cost (credit)	(141)	(218)	(282)	(435)
Amortization of actuarial losses	244	267	505	483
Curtailment loss	0	0	0	4
Net periodic benefit cost	$ 564	$ 618	$ 1,214	$ 1,232