Pension and Other Postretirement Benefits (Details 11) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Defined benefit pension plans [Member]
Pension and other postretirement benefits expenses
Service cost	$ 6,530	$ 5,923	$ 6,155
Interest cost	21,624	22,452	22,943
Expected return on plan assets	(32,827)	(32,041)	(30,938)
Amortization of prior service cost	845	1,124	937
Recognized losses	12,048	5,725	2,495
Curtailment loss gain	0	(1,884)	0
Settlement loss	92	304	0
Net periodic benefit cost	8,312	1,603	1,592
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 2013	16,418
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 (credit) in 2013	814
Other postretirement benefit plans [Member]
Pension and other postretirement benefits expenses
Service cost	273	286	357
Interest cost	2,532	2,831	3,182
Expected return on plan assets	0	0	0
Amortization of prior service cost	(1,585)	(1,541)	(970)
Recognized losses	1,082	806	421
Curtailment loss gain	0	0	(950)
Settlement loss	0	0	0
Net periodic benefit cost	2,302	2,382	2,040
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 2013	1,158
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 (credit) in 2013	$ (1,579)