Income Taxes - Reconciliation of Federal Statutory Rate to Effective Income Tax Rate on Continuing Operations (Detail)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Federal statutory rate	35.00%	35.00%	35.00%
State, net of federal benefit	1.00%	4.00%	5.00%
Recognition of previously unrecognized tax benefits	0.00%	(15.00%)	0.00%
State rate change due to acquisition	0.00%	0.00%	(2.00%)
Acquisition costs	0.00%	0.00%	4.00%
Noncontrolling interests	0.00%	(5.00%)	(7.00%)
Effective Income Tax Rate Reconciliation, Disposition of Asset, Percent	1.00%	0.00%	0.00%
Charitable contributions	(1.00%)	0.00%	0.00%
Oil and gas percentage depletion	(2.00%)	(2.00%)	(5.00%)
Other	0.00%	0.00%	1.00%
Effective tax rate	34.00%	17.00%	31.00%

Effective Income Tax Rate Reconciliation Acquisition Costs

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Effective Income Tax Rate Reconciliation Oil And Natural Gas Percentage Depletion

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Effective Income Tax Rate Reconciliation State Rate Change Due To Acquisition

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Effective Income Tax Rate Reconciliation State Rate Change Due To Previously Unrecognized Tax Benefit

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

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Percentage 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 disposition of an asset.

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