Employee and Retiree Benefit Plans (Effects of Fair Value Measurements Using Significant Unobservable Inputs on Changes in Level 3 Plan Assets) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Insurance [Abstract]
Beginning Balance	$ 32,788	$ 14,654
Actual return on plan assets:
Relating to assets held at the reporting date	1,164	3,134
Purchases, sales and settlements		15,000
Ending Balance	$ 33,952	$ 32,788