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, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Taxes [Abstract]
Income tax provision at the statutory rate	35.00%	35.00%	35.00%
State taxes, net of federal benefit	3.80%	3.70%	3.60%
Deferred income tax liability adjustments	0.30%		1.00%
Noncontrolling interests	(0.10%)		(0.10%)
Other	0.50%	0.20%	0.30%
Effective income tax rate, total	39.50%	38.90%	39.80%