v3.6.0.2
Stock incentive plans - Restricted stock unit awards (Details) - USD ($)
$ / shares in Units, $ in Thousands
12 Months Ended
Dec. 31, 2016
RSUs  
Stock incentive plans  
Vesting period 3 years
Number of Shares  
Non-vested at beginning of year (in shares) 1,819,000
Granted (in shares) 3,200,000
Vested (in shares) (1,054,024)
Canceled/ forfeited (in shares) (140,000)
Non-vested at end of year (in shares) 3,825,000
Weighted Average Grant Date Fair Value  
Non-vested at beginning year (in dollars per share) $ 6.39
Granted (in dollars per share) 6.42
Vested (in dollars per share) 6.85
Canceled/forfeited (in dollars per share) 7.07
Non-vested at end of year (in dollars per share) $ 6.55
Other Disclosures  
Shares of common stock issued resulting from vesting 704,787
Total unrecognized stock-based compensation expense $ 17,831
Weighted average period over which unrecognized compensation expense is expected to be recognized 2 years
Time-based restricted stock unit awards | Executive and non executive personnel | Maximum  
Stock incentive plans  
Vesting period 3 years
Time-based restricted stock unit awards | Existing board members  
Stock incentive plans  
Vesting period 1 year
Time-based restricted stock unit awards | New board members  
Stock incentive plans  
Vesting period 4 years
Vesting percentage when the individual completes 12 months of continuous service 25.00%
Performance-based restricted stock unit awards  
Stock incentive plans  
Vesting period 3 years