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Income Taxes (Differences between Income Tax Provision in Statements of Net Income and Income Tax Provision Computed at Federal Statutory Rate) (Detail)
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Income Taxes [Abstract]      
Income tax provision (benefit) at the statutory rate (35.00%) 35.00% 35.00%
State taxes, net of federal benefit (0.30%) 3.80% 3.70%
Deferred income tax liability adjustments (3.10%) 0.30%  
Noncontrolling interests (0.30%) (0.10%)  
Goodwill impairment 12.30%    
Other 1.40% 0.50% 0.20%
Effective income tax rate, total (25.00%) 39.50% 38.90%