Pension and Other Postretirement Benefits (Details 11) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Defined benefit pension plans [Member]
Pension and other postretirement benefits expenses
Service cost	$ 6,181	$ 6,530	$ 5,923
Interest cost	20,112	21,624	22,452
Expected return on plan assets	(33,144)	(32,827)	(32,041)
Amortization of prior service cost	752	845	1,124
Recognized losses	16,365	12,048	5,725
Curtailment loss gain	199	0	(1,884)
Settlement loss	637	92	304
Special termination benefit	1,016	0	0
Net periodic benefit cost	12,118	8,312	1,603
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	7,733
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	730
Other postretirement benefit plans [Member]
Pension and other postretirement benefits expenses
Service cost	233	273	286
Interest cost	2,061	2,532	2,831
Expected return on plan assets	0	0	0
Amortization of prior service cost	(1,006)	(1,585)	(1,541)
Recognized losses	1,004	1,082	806
Curtailment loss gain	(3,081)	0	0
Settlement loss	0	0	0
Special termination benefit	0	0	0
Net periodic benefit cost	(789)	2,302	2,382
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	813
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	$ (868)