Income Taxes Tax Reconciliation (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2012	Mar. 31, 2011
Income Tax Disclosure [Abstract]
Income Before Income Taxes	$ 40,055	$ 41,753
Income tax calculated at 35% federal statutory rate	(14,019)	(14,614)
Permanent or flow through adjustments:
Flow-through repairs deductions	5,571	3,982
Flow-through of state bonus depreciation deduction	1,371	2,603
Recognition of state net operating loss benefit/valuation allowance release	0	847
State income tax & other, net	(935)	(1,996)
Total permanent or flow-through adjustments	6,007	5,436
Income tax expense	$ (8,012)	$ (9,178)

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Income Tax Reconciliation, Accelerated Tax Depreciation, Flow Through Adjustment

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Income Tax Reconciliation, Reconciling Items, Total

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Income Tax Reconciliation, State Net Operating Loss Carry Forward Utilization Benefit and Valuation Allowance Release

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Sum of operating profit and nonoperating income or expense before Income or Loss from equity method investments, income taxes, extraordinary items, and noncontrolling interest.

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The sum of the current income tax expense or benefit and the deferred income tax expense or benefit pertaining to continuing operations.

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The portion of the difference between total income tax expense or benefit as reported in the Income Statement for the period and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations attributable to other deductions received under enacted tax laws not otherwise listed in the existing taxonomy.

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The amount of income tax expense or benefit for the period computed by applying the domestic federal statutory tax rates to pretax income from continuing operations.

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The portion of the difference, between total income tax expense or benefit as reported in the Income Statement for the period and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations, that is attributable to state and local income tax expense or benefit.

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