Income Taxes (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Income Tax
Income before provision for income tax	$ 101,781	$ 231,006	$ 87,207	$ 251,325
Federal income tax at statutory rate			18,494	33,110
Permanent items			29	16
State income taxes, net of federal benefit			1,482	5,024
Provision on income from Class A units			2,835	10,868
Provision for income tax	16,283	44,473	22,840	49,018
Corporation
Income Tax
Income before provision for income tax			52,839	94,600
Federal statutory income tax rate (as a percent)			35.00%	35.00%
Federal income tax at statutory rate			18,494	33,110
Permanent items			29	16
State income taxes, net of federal benefit			1,321	4,259
Provision on income from Class A units			2,835	10,868
Provision for income tax			22,679	48,253
Partnership
Income Tax
Income before provision for income tax			40,023	154,519
Federal statutory income tax rate (as a percent)			0.00%	0.00%
State income taxes, net of federal benefit			161	765
Provision for income tax			161	765
Eliminations
Income Tax
Income before provision for income tax			$ (5,655)	$ 2,206
Federal statutory income tax rate (as a percent)			0.00%	0.00%

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This element represents the income tax expense (benefit) of a taxable wholly-owned subsidiary based on its share of the entity's income resulting from its ownership of Class A units.

+ References

No definition available.

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- Definition

The domestic federal statutory tax rate applicable under enacted tax laws to the Company's pretax income from continuing operations for the period. The "statutory" tax rate is the regular tax rate if there are alternative tax systems.

+ References

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- Definition

This element represents the income or loss from continuing operations attributable to the economic entity which may also be defined as revenue less expenses from ongoing operations, after income or loss from equity method investments, but before income taxes, extraordinary items, and noncontrolling interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

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- Definition

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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Reference 1: http://www.xbrl.org/2003/role/presentationRef

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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- Definition

The sum of the differences 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 nondeductible expenses under enacted tax laws, or differences in the methodologies used to determine expense amounts for financial statements prepared in accordance with generally accepted accounting principles and enacted tax laws.

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- Definition

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.

+ References

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