Employee Benefit Plans Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Pension Benefits [Member]
Components of Net Periodic Benefit Cost (Income) [Abstract]
Service cost	$ 2,941	$ 2,718	$ 5,880	$ 6,181
Interest cost	6,539	6,545	13,105	13,087
Expected return on plan assets	(7,043)	(7,861)	(14,124)	(15,781)
Amortization of prior service cost	61	61	123	123
Recognized actuarial loss	2,478	2,699	4,944	5,317
Net Periodic Benefit Cost (Income)	4,976	4,162	9,928	8,927
Other Postretirement Benefits [Member]
Components of Net Periodic Benefit Cost (Income) [Abstract]
Service cost	116	134	246	263
Interest cost	196	210	398	393
Expected return on plan assets	(260)	(242)	(521)	(485)
Amortization of prior service cost	(470)	(441)	(941)	(941)
Recognized actuarial loss	71	112	158	193
Net Periodic Benefit Cost (Income)	$ (347)	$ (227)	$ (660)	$ (577)