Employee and Retiree Benefit Plans (Projected Benefit Obligations, Accumulated Benefit Obligations and Fair Value of Plan Assets for Plans where Accumulated Benefit Obligation Exceeded Fair Value of Plan Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Funded Defined Benefit Pension Plans [Member] | Qualified Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected Benefit Obligations	$ 630,587	$ 658,618
Accumulated Benefit Obligations	622,841	597,918
Fair Value of Plan Assets	500,695	533,165
Unfunded Defined Benefit Pension Plans [Member] | Non-Qualified Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected Benefit Obligations	148,019	147,018
Accumulated Benefit Obligations	140,544	127,200
Unfunded Other Postretirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected Benefit Obligations	115,222	118,496
Accumulated Benefit Obligations	$ 115,222	$ 118,496