Quarterly report pursuant to Section 13 or 15(d)

Stock-Based Compensation - Stock Option Activity (Detail)

v2.4.0.8
Stock-Based Compensation - Stock Option Activity (Detail) (USD $)
In Millions, except Share data in Thousands, unless otherwise specified
 6 Months Ended
Jun. 30, 2013
Dec. 31, 2012
Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding [Roll Forward]    
Number of Shares Underlying Options, Outstanding at beginning of period 4,065  
Number of Shares Underlying Options, Granted 1,236  
Number of Shares Underlying Options, Exercised (32)  
Number of Shares Underlying Options, Forfeited     
Number of Shares Underlying Options, Outstanding at end of period 5,269 4,065
Number of Shares Underlying Options, Exercisable at end of period 4,386  
Weighted Average Exercise Price Per Share, Outstanding at beginning of period $ 6.12  
Weighted Average Exercise Price Per Share, Granted $ 7.59  
Weighted Average Exercise Price Per Share, Exercised $ 4.24  
Weighted Average Exercise Price Per Share, Forfeited     
Weighted Average Exercise Price Per Share, Outstanding at end of period $ 6.47 $ 6.12
Weighted Average Exercise Price Per Share, Exercisable at end of period $ 6.15  
Weighted Average Remaining Contractual Term, Granted 4 years 8 months 16 days  
Weighted Average Remaining Contractual Term, Exercised 3 months 11 days  
Weighted Average Remaining Contractual Term, Forfeited     
Weighted Average Remaining Contractual Term, Outstanding balance 2 years 9 months 7 days 2 years 7 months 24 days
Weighted Average Remaining Contractual Term, Exercisable at end of period 2 years 5 months 12 days  
Aggregate Intrinsic Value, Outstanding at end of period $ 6.62  
Aggregate Intrinsic Value, Exercisable at end of period $ 6.62