Summary of Significant Accounting Policies - Difference Between Customary Rate and Effective Tax Rate on Income Before Income Taxes Due (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Effective Income Tax Rate Continuing Operations Tax Rate Reconciliation [Line Items]
Tax at statutory rate	35.00%	35.00%	35.00%	35.00%
Tax effect of:
Nondeductible stock-based compensation	4.20%	0.60%	3.30%	(1.40%)
State income taxes, net of federal benefit	(0.40%)	0.30%	(0.30%)	1.10%
Other	1.00%	(0.10%)	0.80%	(0.20%)
Effective tax rate	39.80%	35.80%	38.80%	34.50%