Employee Benefit Plans Net Periodic Benefit Cost (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Pension Benefits [Member]
Components of Net Periodic Benefit Cost (Income) [Abstract]
Service cost	$ 3,367	$ 2,586	$ 10,100	$ 8,616
Interest cost	5,680	6,016	17,040	17,867
Expected return on plan assets	(8,123)	(7,501)	(24,369)	(22,497)
Amortization of prior service cost	62	62	185	185
Recognized actuarial loss	2,911	2,291	8,735	6,485
Net Periodic Benefit Cost (Income)	3,897	3,454	11,691	10,656
Other Postretirement Benefits [Member]
Components of Net Periodic Benefit Cost (Income) [Abstract]
Service cost	135	162	406	406
Interest cost	219	309	658	875
Expected return on plan assets	(254)	(253)	(764)	(766)
Amortization of prior service cost	(500)	(500)	(1,499)	(1,499)
Recognized actuarial loss	242	234	728	593
Net Periodic Benefit Cost (Income)	$ (158)	$ (48)	$ (471)	$ (391)