Employee Benefit Plans Net Periodic Benefit Cost (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 8,407	$ 6,782	$ 6,196
Interest cost	17,284	18,087	17,740
Expected return on plan assets	(25,477)	(25,819)	(21,651)
Amortization of prior service cost (benefit)	1,308	1,359	1,657
Amortization of losses	17,578	10,372	6,456
Net periodic benefit cost (benefit)	19,100	10,781	10,398
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	918	673	587
Interest cost	956	972	1,029
Expected return on plan assets	0	0	0
Amortization of prior service cost (benefit)	25	69	(5,334)
Amortization of losses	582	570	3,357
Net periodic benefit cost (benefit)	$ 2,481	$ 2,284	$ (361)