Employee Benefit Plans Net Periodic Benefit Cost (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2,419	$ 1,940
Interest cost	4,834	3,989
Expected return on plan assets	(7,424)	(5,879)
Amortization of prior service cost	388	302
Amortization of losses	5,727	4,056
Net periodic benefit cost	5,944	4,408
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	249	210
Interest cost	240	223
Expected return on plan assets	0	0
Amortization of prior service cost	6	6
Amortization of losses	218	144
Net periodic benefit cost	$ 713	$ 583