EQUITY-BASED COMPENSATION - Summary of Non-vested restricted stock award activity (Details 4) - Non-vested restricted stock
shares in Thousands
12 Months Ended
Dec. 31, 2016
$ / shares
shares
Shares  
Outstanding, as of January 1, 2016 | shares 538
Granted | shares 432
Vested | shares (168)
Forfeited | shares (139)
Outstanding, as of December 31, 2016 | shares 663
Weighted Average Grant Date Fair Value  
Outstanding, as of January 1, 2016 | $ / shares $ 9.59
Granted | $ / shares 7.14
Vested | $ / shares 9.12
Forfeited | $ / shares 9.70
Outstanding, as of December 31, 2016 | $ / shares $ 8.08