Income Taxes (Schedule of Effective Tax Rate Reconciliation) (Details 2) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Income tax provision calculated using the federal statutory income tax rate	$ 357,895	$ 224,833	$ 299,900
State income taxes, net of federal income tax benefit	25,368	13,518	30,955
Effect of statutory rate change	4,225	(4,178)	(429)
Other	(422)	(1,390)	1,071
Total income tax expense	$ 387,066us-gaap_IncomeTaxExpenseBenefit	$ 232,783us-gaap_IncomeTaxExpenseBenefit	$ 331,497us-gaap_IncomeTaxExpenseBenefit

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations, attributable to increase (decrease) in the income tax rates.

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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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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to state and local income tax expense (benefit).

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