Pension and Other Postretirement Benefits (Details 11) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Defined benefit pension plans [Member]
Pension and other postretirement benefits expenses
Service cost	$ 5,923	$ 6,155	$ 6,598
Interest cost	22,452	22,943	22,734
Expected return on plan assets	(32,041)	(30,938)	(30,676)
Amortization of prior service cost	1,124	937	944
Recognized losses	5,725	2,495	1,950
Curtailment loss gain	(1,884)	0	71
Settlement loss	304
Special termination benefits	0	0	48
Net periodic benefit cost	1,603	1,592	1,669
Estimated net actuarial loss for the defined benefit pension plans that will be amortized from accumulated other non-owner changes to equity into net periodic benefit cost in 2012	10,986
Estimated prior service cost for the defined benefit pension plans that will be amortized from accumulated other non-owner changes to equity into net periodic benefit cost in 2012	1,083
Other postretirement benefit plans [Member]
Pension and other postretirement benefits expenses
Service cost	286	357	465
Interest cost	2,831	3,182	3,530
Expected return on plan assets	0	0	0
Amortization of prior service cost	(1,541)	(970)	(745)
Recognized losses	806	421	202
Curtailment loss gain	0	(950)	0
Special termination benefits	0	0	0
Net periodic benefit cost	2,382	2,040	3,452
Estimated net actuarial loss for the defined benefit pension plans that will be amortized from accumulated other non-owner changes to equity into net periodic benefit cost in 2012	1,141
Estimated prior service cost for the defined benefit pension plans that will be amortized from accumulated other non-owner changes to equity into net periodic benefit cost in 2012	$ (1,585)