Pension and Other Postretirement Benefits (Details) (USD $) In Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Pensions [Member]
Pension and other postretirement benefits expenses
Service cost	$ 1,375	$ 1,399	$ 2,944	$ 3,106
Interest cost	5,668	5,709	11,240	11,389
Expected return on plan assets	(8,130)	(7,660)	(16,030)	(15,365)
Amortization of prior service cost	287	239	562	459
Recognized losses	1,543	643	2,875	1,222
Net periodic benefit cost	743	330	1,591	811
Other Postretirement Benefits [Member]
Pension and other postretirement benefits expenses
Service cost	48	61	143	187
Interest cost	685	796	1,424	1,632
Amortization of prior service cost	(485)	(246)	(771)	(491)
Recognized losses	240	105	404	215
Curtailment gain	0	0	0	(987)
Net periodic benefit cost	$ 488	$ 716	$ 1,200	$ 556