Income Taxes (Schedule Of Deferred Tax Assets And Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Insurance and claims accruals	$ 74,651	$ 76,596
Allowance for uncollectible accounts	8,260	5,672
Other	14,724us-gaap_DeferredTaxAssetsOther	8,437us-gaap_DeferredTaxAssetsOther
Gross deferred tax assets	97,635us-gaap_DeferredTaxAssetsGross	90,705us-gaap_DeferredTaxAssetsGross
Property and equipment	295,628	282,642
Prepaid expenses	6,913	6,906
Other	2,634us-gaap_DeferredTaxLiabilitiesOther	3,079us-gaap_DeferredTaxLiabilitiesOther
Gross deferred tax liabilities	305,175us-gaap_DeferredTaxLiabilities	292,627us-gaap_DeferredTaxLiabilities
Net deferred tax liability	$ 207,540us-gaap_DeferredTaxAssetsLiabilitiesNet	$ 201,922us-gaap_DeferredTaxAssetsLiabilitiesNet

Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from estimated losses under self insurance.

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Amount of deferred tax liability attributable to taxable temporary differences net of deferred tax asset attributable to deductible temporary differences and carryforwards after valuation allowances.

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Amount of deferred tax liability attributable to taxable temporary differences from property, plant, and equipment.

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