v3.8.0.1
STOCK-BASED COMPENSATION - Restricted Stock Units (Details) - USD ($)
$ / shares in Units, $ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Restricted Stock Units, Weighted Average Grant Date Fair Value [Abstract]        
Aggregate grant date fair value   $ 100   $ 3,000
Payment for shares withheld for tax withholdings on vesting of restricted stock units $ (600) $ (400) $ (1,070) $ (941)
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 180,345 60,638 275,922 156,186
2014 Equity Incentive Plan        
Restricted Stock Units, Number of Shares [Roll Forward]        
Awards granted     3,287,665  
Awards canceled     (1,595,966)  
Restricted Stock Units (RSUs)        
Restricted Stock Units, Number of Shares [Roll Forward]        
Beginning balance     4,365,670  
Awards granted     3,287,665  
Awards vested     (1,453,616)  
Awards canceled     (1,320,044)  
Ending balance 4,879,675   4,879,675  
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) $ 4.66 $ 6.09 4.96 $ 6.23
Awards vested (in dollars per share)     5.92  
Awards canceled (in dollars per share)     6.14  
Ending balance (in dollars per share) $ 5.49   $ 5.49  
Aggregate grant date fair value $ 400 $ 1,000 $ 16,300 $ 19,900
Fair value of shares vested $ 1,700 $ 4,100 $ 6,300 $ 10,000
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