Employee Benefit Plans Net Periodic Benefit Cost (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 6,782	$ 6,196	$ 6,489
Interest cost	18,087	17,740	18,082
Expected return on plan assets	(25,819)	(21,651)	(21,427)
Amortization of prior service cost (benefit)	1,359	1,657	1,830
Amortization of losses	10,372	6,456	6,196
Net periodic benefit cost (benefit)	10,781	10,398	11,170
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	673	587	482
Interest cost	972	1,029	1,144
Expected return on plan assets	0	0	0
Amortization of prior service cost (benefit)	69	(5,334)	(9,480)
Amortization of losses	570	3,357	5,841
Net periodic benefit cost (benefit)	$ 2,284	$ (361)	$ (2,013)