Pension and Other Postretirement Benefits Net Periodic Benefit Cost (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Pension Plans, Defined Benefit
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 6,030	$ 5,554	$ 18,089	$ 16,661
Interest cost	5,979	6,224	17,936	18,672
Expected return on plan assets	(5,977)	(5,918)	(17,931)	(17,753)
Amortization of net actuarial loss	6,593	5,279	19,778	15,837
Amortization of prior service cost (gain)	343	346	1,031	1,036
Net periodic benefit cost	12,968	11,485	38,903	34,453
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	661	584	1,983	1,752
Interest cost	718	838	2,154	2,516
Expected return on plan assets	0	0	0	0
Amortization of net actuarial loss	449	430	1,346	1,290
Amortization of prior service cost (gain)	(545)	(546)	(1,635)	(1,636)
Net periodic benefit cost	$ 1,283	$ 1,306	$ 3,848	$ 3,922