Annual report pursuant to Section 13 and 15(d)

Stock-based Compensation Plans and Awards - Schedule of activities for RSUs, MSUs and PSUs (Details)

v3.8.0.1
Stock-based Compensation Plans and Awards - Schedule of activities for RSUs, MSUs and PSUs (Details) - $ / shares
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Number      
Granted (in shares) 2,226,443    
RSUs      
Number      
Unvested at the beginning of the period (in shares) 22,404,417    
Granted (in shares) 13,627,053    
Vested (in shares) (9,478,804)    
Forfeited (in shares) (7,277,071)    
Unvested at the end of the period (in shares) 19,275,595 22,404,417  
Expected to vest at end of the period (in shares) 19,275,595    
Weighted-Average Grant Date Fair Value      
Unvested at the beginning of the period (in dollars per share) $ 13.26    
Granted (in dollars per share) 10.13    
Vested (in dollars per share) 13.80    
Forfeited (in dollars per share) 12.16    
Unvested at the end of the period (in dollars per share) 11.19 $ 13.26  
Expected to vest at end of the period (in dollars per share) $ 11.19    
MSUs      
Number      
Unvested at the beginning of the period (in shares) 533,383    
Granted (in shares) 0 0 776,000
Forfeited (in shares) (217,387)    
Unvested at the end of the period (in shares) 315,996 533,383  
Expected to vest at end of the period (in shares) 113,672    
Weighted-Average Grant Date Fair Value      
Unvested at the beginning of the period (in dollars per share) $ 5.49    
Forfeited (in dollars per share) 5.64    
Unvested at the end of the period (in dollars per share) 5.38 $ 5.49  
Expected to vest at end of the period (in dollars per share) $ 5.38    
PSUs      
Number      
Unvested at the beginning of the period (in shares) 1,835,250    
Granted (in shares) 0 1,835,250 0
Forfeited (in shares) (665,782)    
Unvested at the end of the period (in shares) 1,169,468 1,835,250  
Expected to vest at end of the period (in shares) 544,392    
Weighted-Average Grant Date Fair Value      
Unvested at the beginning of the period (in dollars per share) $ 5.33    
Forfeited (in dollars per share) 5.55    
Unvested at the end of the period (in dollars per share) 5.21 $ 5.33  
Expected to vest at end of the period (in dollars per share) $ 5.09