Employee Benefit Plans Net Periodic Benefit Cost (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2,011	$ 2,102	$ 4,430	$ 4,042
Interest cost	3,953	4,321	8,787	8,309
Expected return on plan assets	(5,966)	(6,369)	(13,390)	(12,248)
Amortization of prior service cost	322	327	710	629
Amortization of losses	4,791	4,394	10,516	8,451
Net periodic benefit cost	5,111	4,775	11,053	9,183
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	249	227	498	437
Interest cost	240	242	480	465
Expected return on plan assets	0	0	0	0
Amortization of prior service cost	6	6	13	12
Amortization of losses	218	156	436	299
Net periodic benefit cost	$ 713	$ 631	$ 1,427	$ 1,213