Summary of Significant Accounting Policies - Difference Between Customary Rate and Effective Tax Rate on Income (Loss) Before Income Taxes Due (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Effective Income Tax Rate Continuing Operations Tax Rate Reconciliation [Line Items]
Tax at statutory rate	35.00%	35.00%	35.00%	35.00%
State income taxes net of federal benefit	2.00%	5.50%	2.10%	(5.50%)
Nondeductible stock-based compensation		(15.10%)	(0.10%)	20.10%
Other		(4.90%)		6.00%
Effective tax rate	5.30%	20.50%	16.00%	55.60%
Federal
Effective Income Tax Rate Continuing Operations Tax Rate Reconciliation [Line Items]
Valuation allowance on deferred tax assets	(31.00%)		(19.80%)
State
Effective Income Tax Rate Continuing Operations Tax Rate Reconciliation [Line Items]
Valuation allowance on deferred tax assets	(0.70%)		(1.20%)