v3.7.0.1
STOCK-BASED COMPENSATION - Restricted Stock Units (Details) - USD ($)
$ / shares in Units, $ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2017
Jun. 30, 2016
Jun. 30, 2017
Jun. 30, 2016
Restricted Stock Units, Weighted Average Grant Date Fair Value [Abstract]        
Aggregate grant date fair value   $ 2,600   $ 2,800
Payment for shares withheld for tax withholdings on vesting of restricted stock units $ (100) $ (200) $ (451) $ (540)
PBRSU to common stock, conversion ratio 100.00%   100.00%  
Market-Based Restricted Stock Unit, Conversion Ratio 100.00%   100.00%  
Common Stock        
Restricted Stock Units, Weighted Average Grant Date Fair Value [Abstract]        
Shares repurchased for tax withholdings on vesting of RSUs 25,209 36,758 95,577 95,548
2014 Equity Incentive Plan        
Restricted Stock Units, Number of Shares [Roll Forward]        
Awards granted     3,191,974  
Awards canceled     (1,203,643)  
Restricted Stock Units (RSUs)        
Restricted Stock Units, Number of Shares [Roll Forward]        
Beginning balance     4,365,670  
Awards granted     3,191,974  
Awards vested     (970,734)  
Awards canceled     (1,108,066)  
Ending balance 5,478,844   5,478,844  
Restricted Stock Units (RSUs) | 2014 Equity Incentive Plan        
Restricted Stock Units, Weighted Average Grant Date Fair Value [Abstract]        
Beginning balance (in dollars per share)     $ 6.23  
Awards granted (in dollars per share) $ 4.96 $ 6.43 4.97 $ 6.24
Awards vested (in dollars per share)     5.09  
Awards canceled (in dollars per share)     6.20  
Ending balance (in dollars per share) $ 5.55   $ 5.55  
Aggregate grant date fair value $ 11,800 $ 16,900 $ 15,900 $ 19,000
Fair value of shares vested $ 2,400 $ 3,400 $ 4,600 $ 5,900
Restricted Stock Units (RSUs) | Vesting period, one year        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Vesting period     1 year  
Restricted Stock Units (RSUs) | Vesting period, three years        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Vesting period     3 years  
PBRSUs        
Restricted Stock Units, Number of Shares [Roll Forward]        
Awards granted     378,644  
Market-Based Restricted Stock Unit [Member]        
Restricted Stock Units, Number of Shares [Roll Forward]        
Awards granted     358,000  
Restricted Stock Units, Weighted Average Grant Date Fair Value [Abstract]        
Awards granted (in dollars per share)     $ 4.18