Investments (Narrative) (Details) (USD $)			12 Months Ended
	Dec. 31, 2011	Dec. 25, 2010	Dec. 25, 2010 Bond Portfolio [Member]	Dec. 31, 2011 Current Investments [Member]	Dec. 31, 2011 Non-Current Investments [Member]	Dec. 31, 2011 Guarantee Payment Of Insurance Claims [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, maximum maturity period, years			5
Unrealized gains on the investments	$ 786,000	$ 760,000
Investments providing collateral for letters of credit to guarantee insurance claims				27,944,000	22,239,000
Letters of credit issued						$ 45,165,000