Annual report pursuant to Section 13 and 15(d)

Stock-Based Compensation, Employee Benefit Plans and Convertible Preferred Stock - Additional Information (Detail)

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Stock-Based Compensation, Employee Benefit Plans and Convertible Preferred Stock - Additional Information (Detail) (USD $)
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Common stock, shares authorized 550,000,000 550,000,000  
Aggregate repurchase price $ 12,076,000    
Restricted stock units issued 1,000,000    
Stock based compensation expense Exchange Offer 7,300,000    
Incremental value attributed to the modified options 1,800,000    
Accrual of bonus awards recorded for employees 5,000,000    
Stock-based compensation expenses related to non-employee 80,000 200,000 200,000
Intrinsic value of options exercised 2,100,000 6,700,000 5,200,000
Intrinsic value of restricted stock units, vested 3,200,000 700,000  
Intrinsic value of restricted stock units, outstanding 20,900,000    
Unvested restricted stock units [Member]
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Total unrecognized compensation cost 21,800,000    
Weighted average period over equity awards expected to vest 2 years 10 months 24 days    
Restricted stock awards [Member]
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Total unrecognized compensation cost 21,800,000    
Weighted average period over equity awards expected to vest 2 years 10 months 24 days    
Unvested stock options [Member]
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Total unrecognized compensation cost $ 3,600,000    
Weighted average period over equity awards expected to vest 2 years 11 months 1 day    
Restricted stock awards [Member]
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Restricted stock awards vested 0 0 0
2010 Equity Incentive Plan [Member]
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Increase in common stock reserved for issuance 2,600,000    
Vesting period 4 years    
Term of option granted, minimum 7 years    
Term of option granted, maximum 10 years    
2010 Equity Incentive Plan [Member] | Restricted stock units [Member]
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting period 4 years    
2010 Employee Stock Purchase Plan [Member]
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Increase in common stock reserved for issuance 1,000,000    
Contribution of earnings by employees 15.00%    
Percentage of purchase of common stock 85.00%    
Percentage of common stock on the date of purchase 85.00%    
Class A common stock [Member]
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Common stock, shares authorized 500,000,000 500,000,000  
Voting rights per share 1    
Number of convertible common stock 1    
Number of shares repurchase and retirement 1,152,000    
Eligible options to purchase shares 1,300,000    
Conversion of preferred stock to common stock     1,491,000
Class A common stock [Member] | 2010 Equity Incentive Plan [Member]
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Percentage of outstanding shares of common stock 4.00%    
Class A common stock [Member] | 2010 Employee Stock Purchase Plan [Member]
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Percentage of outstanding shares of common stock 1.25%    
Class B common stock [Member]
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Common stock, shares authorized 500,000,000 500,000,000  
Voting rights per share 10    
Right to elect as Class B Director 2    
Number of shares repurchase and retirement 1,000,000    
Eligible options to purchase shares 600,000    
Conversion of preferred stock to common stock     13,035,000
Series A Preferred Stock and Series B Preferred Stock [Member]
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Aggregate amount of conversion of Preferred Stock     14,500,000