Income Taxes (Summary Of Temporary Differences That Give Rise To Deferred Income Tax Assets And Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Income Tax Expense (Benefit) [Abstract]
Inventory costing and valuation methods	$ 4,045	$ 4,643
Allowance for doubtful accounts receivable	2,618	2,202
Insurance claims payable	7,825	10,807
Promotions payable	945	797
Accrued legal reserves	207	39
Stock based compensation	4,715	5,853
Federal and state benefit of uncertain tax positions	1,871	1,632
Other, net	267	920
Total deferred income tax assets	22,493	26,893
Property and equipment	(59,371)	(48,329)
Total deferred income tax liabilities	(59,371)	(48,329)
Net deferred income tax asset (liability)	$ (36,878)	$ (21,436)