Supplemental equity information (Details 1) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 25, 2012
Accumulated Other Comprehensive Income [Line Items]
Balance at	$ (701,141)	$ (595,839)
Other comprehensive income before reclassifications	(17,889)	8,134
Amounts reclassified from accumulated other comprehensive income	9,696	7,086
Other comprehensive income	(8,193)	15,220
Balance at	(709,334)	(580,619)
Retirement Plans [Member]
Accumulated Other Comprehensive Income [Line Items]
Balance at	(1,119,263)	(995,853)
Other comprehensive income before reclassifications	14,697	(2,873)
Amounts reclassified from accumulated other comprehensive income	9,696	7,086
Other comprehensive income	24,393	4,213
Balance at	(1,094,870)	(991,640)
Foreign Currency Translation [Member]
Accumulated Other Comprehensive Income [Line Items]
Balance at	418,122	400,014
Other comprehensive income before reclassifications	(32,586)	11,007
Amounts reclassified from accumulated other comprehensive income	0	0
Other comprehensive income	(32,586)	11,007
Balance at	$ 385,536	$ 411,021