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Income Taxes - Additional Information (Detail) (USD $)
 12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Income Tax Contingency [Line Items]      
U.S. federal tax statutory rate 35.00% 35.00% 35.00%
Estimated net deferred tax expense     $ 35,600,000
Net operating loss 7,700,000    
Current income tax paid 7,000      
Net operating loss expiration year Its statute of limitation for the year ended December 31, 2012 will expire in 2016    
Deferred tax asset related to net operating loss carryforwards 13,926,000 13,110,000  
Unrealized excess tax benefits from stock-based compensation 1,000,000    
Unrealized excess tax benefits of stock-based compensation 2,700,000    
Unrecognized tax benefits 0    
Earliest open year for audit by the IRS of any state jurisdiction 2010    
Net current deferred tax asset (liability) (4,600,000) 3,200,000  
Domestic Tax Authority [Member]
      
Income Tax Contingency [Line Items]      
Net operating loss 39,900,000    
Net operating loss expiration year Expire between 2030 and 2032    
State and Local Jurisdiction [Member]
      
Income Tax Contingency [Line Items]      
Net operating loss $ 25,600,000    
Net operating loss expiration year Expire between 2017 and 2032