Income Taxes - U.S. Federal Statutory Income Tax Rate Reconciled to Effective Rate (Detail)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Income tax expense at U.S. federal statutory rate	35.00%	35.00%	35.00%
Federal tax credits	(3.21%)	(11.74%)	(4.13%)
Taxing authority audit settlements and other tax adjustments	(1.59%)	(3.56%)	(0.02%)
Noncontrolling interests	(0.81%)	(2.28%)	(1.16%)
State and local income taxes, net of federal income tax benefit	1.77%	9.81%	3.85%
Tax rate differential on foreign income	(0.46%)	1.63%	(0.96%)
Tax impact of impairments	0.46%	41.95%	0.57%
Tax impact of divestitures	(7.89%)
Other	0.34%	2.94%	0.80%
Provision for income taxes	23.61%	73.75%	33.95%

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 a business not qualifying as a discontinued operation.

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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 statutory income tax expense (benefit) outside of the country of domicile.

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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 noncontrolling interest income (loss) exempt from income taxes.

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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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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 income tax settlements. Including, but not limited to, domestic tax settlement, foreign tax settlement, state and local tax settlement, and other tax settlements.

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