Pension Benefits - Schedule of Assumptions Used (Details) - Pension Plan [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 25, 2016	Dec. 27, 2015
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Calculation term, market-related value	3 years
Increase (decrease) to pension obligation due to change in mortality table assumptions	$ 15.4	$ 34.7
Decrease in service costs and interest costs		$ 18.0
Nonqualified Plan [Member]
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Discount rate	3.67%	4.17%
Rate of increase in compensation levels	2.50%	2.50%
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate for determining projected benefit obligation	4.17%	4.40%	3.90%
Discount rate in effect for determining interest cost	3.39%	3.44%	3.90%
Rate of increase in compensation levels	2.50%	2.50%	2.50%
Qualified Plan [Member]
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Discount rate	3.75%	4.31%
Rate of increase in compensation levels	2.95%	2.95%
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate for determining projected benefit obligation	4.31%	4.60%	4.05%
Discount rate in effect for determining service cost	4.74%	5.78%	4.05%
Discount rate in effect for determining interest cost	3.54%	3.68%	4.05%
Rate of increase in compensation levels	2.95%	2.91%	2.89%
Expected long-term rate of return on assets	6.73%	7.01%	7.01%