Pension and Other Postretirement Benefits (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Pensions [Member]
Pension and other postretirement benefits expenses
Service cost	$ 1,374	$ 1,132	$ 4,126	$ 3,439
Interest cost	4,976	5,455	14,968	16,432
Expected return on plan assets	(8,048)	(8,476)	(24,207)	(25,529)
Amortization of prior service cost (credit)	76	152	231	486
Amortization of actuarial losses	3,730	2,141	11,215	6,374
Curtailment loss	0	0	0	219
Settlement loss	0	281	0	863
Special termination benefits	0	0	0	715
Net periodic benefit cost	2,108	685	6,333	2,999
Other Postretirement Benefits [Member]
Pension and other postretirement benefits expenses
Service cost	36	29	109	110
Interest cost	459	540	1,377	1,638
Amortization of prior service cost (credit)	(141)	(218)	(423)	(653)
Amortization of actuarial losses	253	268	758	751
Curtailment loss	0	0	0	4
Net periodic benefit cost	$ 607	$ 619	$ 1,821	$ 1,850