v2.4.0.8
Redeemable Convertible Preferred Stock and Shareholders' Deficit - Summary of Aggregate Redemption of Shares (Detail) (USD $)
Dec. 31, 2012
Dec. 31, 2011
Series E Redeemable Convertible Preferred Stock [Member]
   
Temporary Equity [Line Items]    
Aggregate redemption price per share $ 5.62 $ 5.41
Series D Redeemable Convertible Preferred Stock [Member]
   
Temporary Equity [Line Items]    
Aggregate redemption price per share $ 3.86 $ 3.64
Series C-3 Redeemable Convertible Preferred Stock [Member]
   
Temporary Equity [Line Items]    
Aggregate redemption price per share $ 2.24 $ 2.12
Series C-2 Redeemable Convertible Preferred Stock [Member]
   
Temporary Equity [Line Items]    
Aggregate redemption price per share $ 2.40 $ 2.26
Series C-1 Redeemable Convertible Preferred Stock [Member]
   
Temporary Equity [Line Items]    
Aggregate redemption price per share $ 2.15 $ 2.03
Series C Redeemable Convertible Preferred Stock [Member]
   
Temporary Equity [Line Items]    
Aggregate redemption price per share $ 1.58 $ 1.49
Series B-1 Redeemable Convertible Preferred Stock [Member]
   
Temporary Equity [Line Items]    
Aggregate redemption price per share $ 1.14 $ 1.09
Series B Redeemable Convertible Preferred Stock [Member]
   
Temporary Equity [Line Items]    
Aggregate redemption price per share $ 1.02 $ 0.98
Series A Redeemable Convertible Preferred Stock [Member]
   
Temporary Equity [Line Items]    
Aggregate redemption price per share $ 1.99 $ 1.88