Benefit Plans Benefit Plans Post Retirement Medical Plan Additional Information (Details) - 6 months ended Jun. 30, 2015 - age	Total
Compensation and Retirement Disclosure [Abstract]
Post-retirement medical, maximum age of coverage	65
Post-retirement medical, minimum service requirement	5 years
Post-retirement medical, minimum age of coverage	55
Post-retirement medical, post 55, pre 2006 employee percentage of monthly insurance	20.00%
Post-retirement medical, post 55, post 2006 employee percentage of monthly insurance	100.00%
Post-retirement medical, post 2006 reduction in premium service requirement	10 years
Post-retirement medical, post 55 with post 2006 reduction in premium service requirement percentage of monthly insurance	50.00%