Pension and Other Postretirement Benefits (Details) (USD $) In Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Pensions [Member]
Pension and other postretirement benefits expenses
Service cost	$ 1,477	$ 1,502	$ 4,421	$ 4,608
Interest cost	5,626	5,697	16,866	17,086
Expected return on plan assets	(8,030)	(7,703)	(24,060)	(23,068)
Amortization of prior service cost	280	239	842	697
Recognized losses	1,436	614	4,311	1,837
Net periodic benefit cost	789	349	2,380	1,160
Other Postretirement Benefits [Member]
Pension and other postretirement benefits expenses
Service cost	70	85	213	272
Interest cost	712	786	2,136	2,418
Amortization of prior service cost	(385)	(236)	(1,156)	(727)
Recognized losses	202	88	606	303
Curtailment gain	0	0	0	(987)
Net periodic benefit cost	$ 599	$ 723	$ 1,799	$ 1,279