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Other Postretirement Benefits - Schedule of Health Care Cost Trend Rates (Details) - Other Postretirement Benefit Plans, Defined Benefit [Member]
12 Months Ended
Dec. 25, 2016
Dec. 27, 2015
Other Postretirement Benefits    
Health care cost trend rate 8.00% 7.20%
Rate to which the cost trend rate is assumed to decline (ultimate trend rate) 5.00% 5.00%
Year that the rate reaches the ultimate trend rate 2025 2023