Fair Value Measurements and Financial Instruments (Details) (Fair value, measurements, recurring [Member], USD $) In Thousands, unless otherwise specified	Sep. 29, 2012	Dec. 31, 2011
Quoted prices in active markets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets invested for self-insurance, classified as other assets, noncurrent	$ 14,429	$ 13,064
Fuel derivatives, classified as other current assets	0
Interest rate swaps, classified as accrued expenses		0
Fuel derivatives, classified as accrued expenses		0
Fuel derivatives, classified as other noncurrent liabilities	0	0
Deferred compensation	0	0
Significant other observable inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets invested for self-insurance, classified as other assets, noncurrent	0	0
Fuel derivatives, classified as other current assets	109
Interest rate swaps, classified as accrued expenses		123
Fuel derivatives, classified as accrued expenses		108
Fuel derivatives, classified as other noncurrent liabilities	66	317
Deferred compensation	853	684
Significant unobservable inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets invested for self-insurance, classified as other assets, noncurrent	0	0
Fuel derivatives, classified as other current assets	0
Interest rate swaps, classified as accrued expenses		0
Fuel derivatives, classified as accrued expenses		0
Fuel derivatives, classified as other noncurrent liabilities	0	0
Deferred compensation	0	0
Carrying (Reported) Amount, Fair Value Disclosure [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets invested for self-insurance, classified as other assets, noncurrent	14,429	13,064
Fuel derivatives, classified as other current assets	109
Interest rate swaps, classified as accrued expenses		123
Fuel derivatives, classified as accrued expenses		108
Fuel derivatives, classified as other noncurrent liabilities	66	317
Deferred compensation	$ 853	$ 684