Retirement And Benefit Plans (Changes In Plan Assets And Benefit Obligations Recognized In Other Comprehensive Income) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 25, 2010	Dec. 26, 2009
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated other comprehensive (income) loss at beginning of year	$ 406,465	$ 440,206
Net loss (gain)	159,118	(20,502)
Amortization of net loss	(17,371)	(13,239)	(10,330)
Amortization of prior service credits
Canadian rate adjustment
Accumulated other comprehensive (income) loss at end of year	548,212	406,465	440,206
Other Defined Benefits Postretirement [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated other comprehensive (income) loss at beginning of year	(20,093)	(26,627)
Net loss (gain)	(1,334)	2,634
Amortization of net loss	(220)	(224)	(147)
Amortization of prior service credits	4,009	4,006	4,001
Canadian rate adjustment	(14)	118
Accumulated other comprehensive (income) loss at end of year	$ (17,652)	$ (20,093)	$ (26,627)