Pension Benefits - Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 25, 2011	Dec. 26, 2010	Dec. 27, 2009
Pension Benefits
Effect of curtailments	$ 0	$ 1,083
Defined contribution plan, cost recognized	23,000	23,000	14,000
Incremental employer contribution percentage based on employee's eligible earnings			3.00%
Pension Plans, Defined Benefit [Member]
Pension Benefits
Defined benefit plan,net gain (loss)	255,907	122,879	(69,416)
Prior service cost	0	0	2,115
Recognized actuarial loss	(28,995)	(20,599)	(25,962)
Amortization of prior service cost/(credit)	(803)	(803)	4,166
Effect of curtailments	0	(1,083)	(2,375)
Total recognized in other comprehensive loss	226,109	100,394	(91,472)
Net periodic pension cost/(income)	45,008	37,843	1,613
Total recognized in net periodic benefit cost and other comprehensive loss	271,117	138,237	(89,859)
Estimated actuarial loss that will be amortized from accumulated other comprehensive loss into net periodic pension cost over the next fiscal year	34,000
Estimated prior service cost that will be amortized from accumulated other comprehensive loss into net periodic pension cost over the next fiscal year	$ 1,000