Quarterly report pursuant to Section 13 or 15(d)

COMMON AND PREFERRED STOCK - Narrative (Details)

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COMMON AND PREFERRED STOCK - Narrative (Details) - USD ($)
 3 Months Ended 12 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Dec. 31, 2018
May 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Total shares of preferred and common stock authorized for issuance (shares) 680,000,000      
Common stock, shares authorized (in shares) 675,000,000   675,000,000  
Common stock, par value (in dollars per share) $ 0.001   $ 0.001  
Preferred stock, shares authorized (in shares) 5,000,000   5,000,000  
Preferred stock, par value (in dollars per share) $ 0.001   $ 0.001  
Stock Activity [Abstract]        
Fair value of common stock surrendered by certain employees to cover tax obligations $ 0 $ 1,000    
Stock Repurchase Program [Abstract]        
Stock repurchase program, amount approved       $ 150,000,000.0
Stock repurchased (in shares) 5,635,000 0 7,360,000  
Repurchase of stock $ 16,300,000      
Repurchase of stock recorded as a settlement of contingent consideration liabilities $ 1,200,000      
Certain employees        
Stock Activity [Abstract]        
Common stock surrendered by certain employees to cover tax obligations (shares) 200,000      
Fair value of common stock surrendered by certain employees to cover tax obligations $ 600,000