Pension and Other Postretirement Benefits (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Pensions [Member]
Pension and other postretirement benefits expenses
Service cost	$ 1,704	$ 1,477	$ 4,962	$ 4,421
Interest cost	5,419	5,626	16,156	16,866
Expected return on plan assets	(8,216)	(8,030)	(24,506)	(24,060)
Amortization of prior service cost (credit)	209	280	629	842
Recognized losses	3,170	1,436	9,029	4,311
Settlement loss	91	0	91	0
Net periodic benefit cost	2,377	789	6,361	2,380
Other Postretirement Benefits [Member]
Pension and other postretirement benefits expenses
Service cost	69	70	205	213
Interest cost	643	712	1,902	2,136
Amortization of prior service cost (credit)	(396)	(385)	(1,189)	(1,156)
Recognized losses	269	202	811	606
Net periodic benefit cost	$ 585	$ 599	$ 1,729	$ 1,799