Employee Benefit Plans Net Periodic Benefit Cost (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1,940	$ 1,695
Interest cost	3,989	4,522
Expected return on plan assets	(5,879)	(6,455)
Amortization of prior service cost	302	340
Amortization of losses	4,056	2,593
Net periodic benefit cost	4,408	2,695
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	210	182
Interest cost	223	236
Expected return on plan assets	0	0
Amortization of prior service cost	6	22
Amortization of losses	144	66
Net periodic benefit cost	$ 583	$ 506