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Company's Restricted Shares Activity Under 2007 Stock Incentive Scheme (Detail) (Stock Incentive Plan 2007, Restricted Stock Units (RSUs), USD $)
12 Months Ended
Dec. 31, 2011
Stock Incentive Plan 2007 | Restricted Stock Units (RSUs)
 
Number of restricted shares  
Outstanding, beginning of period 777,000
Granted 12,670,000
Exercised (155,400)
Forfeited/Cancelled (136,000)
Outstanding, end of period 13,155,600
Vested and expected to vest as of end of period 12,382,299
Weighted average grant date fair value  
Outstanding, beginning of period $ 5,440,896
Granted $ 40,299,824
Exercised $ (1,149,096)
Forfeited/Cancelled $ (945,200)
Outstanding, end of period $ 43,646,424
Vested and expected to vest as of December 31, 2011 $ 41,166,971