Other Postretirement Benefits - Changes in the Benefit Obligations Recognized in Other Comprehensive Income (Details) (USD $)	3 Months Ended	12 Months Ended
	Mar. 25, 2012	Dec. 29, 2013	Dec. 30, 2012	Dec. 25, 2011
Other Postretirement Benefits
Additional postretirement costs		$ 20,000,000	$ 18,000,000	$ 16,000,000
Other Postretirement Benefit Plans, Defined Benefit [Member]
Other Postretirement Benefits
Net actuarial loss/(gain)		(13,500,000)	11,562,000	13,436,000
Prior service credit		(1,690,000)	0	(35,712,000)
Recognized actuarial loss		(4,440,000)	(3,328,000)	(2,289,000)
Amortization of prior service credit		13,051,000	15,112,000	16,593,000
Effect of curtailment	27,200,000	49,122,000	27,213,000	0
Total recognized in other comprehensive (income)/loss		42,543,000	50,559,000	(7,972,000)
Net periodic pension cost/(income)		(52,543,000)	(33,055,000)	(6,270,000)
Total recognized in net periodic benefit cost and other comprehensive loss		(10,000,000)	17,504,000	(14,242,000)
Estimated actuarial loss that will be amortized from accumulated other comprehensive loss into net periodic pension cost over the next fiscal year		5,000,000
Estimated prior service cost that will be amortized from accumulated other comprehensive loss into net periodic pension cost over the next fiscal year		$ 6,000,000