Pension Benefits - Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Details) - Pension Plan [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2018	Dec. 31, 2017	Dec. 25, 2016
Pension Benefits
Net actuarial loss/(gain)	$ 29,965	$ 22,600	$ (4,289)
Amortization of loss	(31,916)	(33,369)	(32,458)
Amortization of prior service credit	1,945	1,945	1,945
Effect of settlement	(421)	(102,109)	(21,294)
Total recognized in other comprehensive (income)/loss	(427)	(110,933)	(56,096)
Net periodic pension cost	18,083	109,014	22,648
Total recognized in net periodic benefit cost and other comprehensive (income)/loss	17,656	(1,919)	(33,448)
Estimated actuarial loss that will be amortized from accumulated other comprehensive loss into net periodic pension cost over the next fiscal year	23,000
Estimated prior service credit that will be amortized from accumulated other comprehensive loss into net periodic pension cost over the next fiscal year	2,000
Defined contribution plan, cost recognized	$ 22,000	$ 23,000	$ 15,000