Equity (Details) (USD $) In Thousands, except Share data in Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 25, 2010
Equity [Abstract]
Cumulative foreign currency translation adjustment	$ (10,396)	$ (9,480)
Unrecognized prior service cost, net of income tax	(13)	(13)
Unrecognized actuarial net loss, net of income tax	(38,667)	(28,289)
Unrecognized derivative gains, net of income tax	(422)	566
Unrealized gain on marketable securities, net of income tax	89	170
Accumulated other comprehensive loss	$ (49,409)	$ (37,046)
Authorization to repurchase shares of common stock (in shares)	10
Shares repurchased (in shares)	2.4
Decrease in Mexican peso value relative to US dollar (in hundredths)	11.40%