Pension Benefits - Schedule of Accumulated Benefit Obligations In Excess of Fair Value (Details) - USD ($) $ in Thousands	Dec. 25, 2016	Dec. 27, 2015
Defined Benefit Plan, Pension Plans with Accumulated Benefit Obligations in Excess of Plan Assets [Abstract]
Projected benefit obligation	$ 2,039,051	$ 2,098,997
Accumulated benefit obligation	2,034,636	2,092,600
Fair value of plan assets	$ 1,576,760	$ 1,579,356