Fair Value Measurements and Financial Instruments Fair Value of Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended										3 Months Ended		9 Months Ended
	Sep. 29, 2012	Dec. 31, 2011	Sep. 29, 2012 Carrying Value [Member]	Dec. 31, 2011 Carrying Value [Member]	Sep. 29, 2012 Fair Value [Member]	Dec. 31, 2011 Fair Value [Member]	Sep. 29, 2012 Longest remaining term, in months [Member]	Dec. 31, 2011 Longest remaining term, in months [Member]	Sep. 29, 2012 Notional hedged volume, in thousands of gallons [Member] gal	Dec. 31, 2011 Notional hedged volume, in thousands of gallons [Member] gal	Sep. 29, 2012 Change During Period, Fair Value Disclosure [Member]	Oct. 01, 2011 Change During Period, Fair Value Disclosure [Member]	Sep. 29, 2012 Change During Period, Fair Value Disclosure [Member]	Oct. 01, 2011 Change During Period, Fair Value Disclosure [Member]
Liabilities, Fair Value Disclosure [Abstract]
Revolving credit facility, noncurrent			$ 27,500	$ 20,000	$ 27,500	$ 20,000
Senior unsecured notes	30,000	30,000	30,000	30,000	30,158	29,925
Term loans, noncurrent			588	1,136	588	1,135
Total			58,088	51,136	58,246	51,060
Interest Rate Derivatives, at Fair Value, Net [Abstract]
Liability fair value of interest rate swaps classified as accrued expenses			0	123
Notional amount of long-term debt hedged			0	10,000
Price Risk Derivatives [Abstract]
Asset fair value of fuel derivatives, classified as other current assets			109	0
Liability fair value of fuel derivatives, classified as accrued expenses			0	108
Liability fair value of fuel derivatives, classified as other noncurrent liabilities			66	317
Longest remaining term, in months							15 months	24 months
Notional hedged volume, in thousands of gallons									1,600,000	2,500,000
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net [Abstract]
Hedge gains, recognized in other comprehensive income	123										0	244	123	685
Gain (Loss) on Fair Value Hedges Recognized in Earnings [Abstract]
Change in fair value, recognized in results of operations, as an (increase in)/decrease in operating costs and expenses											$ 616	$ 809	$ 650	$ 787