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Employee Benefit Plans Assumed Health Care Cost Trent Rates for Medical Plans (Details) - Other Postretirement Benefit Plan
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]      
Medical cost trend rate 6.50% 7.00% 7.50%
Ultimate medical cost trend rate 5.00% 5.00% 5.00%
Year ultimate medical cost trend rate will be reached 2019 2019 2019