Reconciliation between Federal Statutory Rate and Effective Tax Rate (Detail)	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Federal statutory rate	35.00%	35.00%	35.00%
State taxes, net of federal income tax benefit	2.30%	2.30%	2.50%
Divestiture gain	0.00%	0.00%	0.30%
Other items	(0.60%)	0.00%	0.40%
Impact of income attributable to noncontrolling interests	(2.20%)	(2.40%)	(1.90%)
Effective tax rate	34.50%	34.90%	36.30%

Effective income tax rate reconciliation impact of income attributable to noncontrolling interest.

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- Definition

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

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 50
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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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-Publisher FASB
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-Topic 740
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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 a business not qualifying as a discontinued operation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Topic 740
-SubTopic 10
-Section S99
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-Subparagraph (SAB TOPIC 6.I)
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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 applicable to state and local income tax expense (benefit), net of federal tax expense (benefit).

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