ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - IPO (Details)
$ / shares in Units, $ in Millions
3 Months Ended
May 16, 2019
shares
Mar. 31, 2019
USD ($)
$ / shares
shares
Dec. 31, 2018
shares
IPO      
Convertible preferred stock, outstanding (in shares)   7,538,671 7,095,746
IPO      
IPO      
Shares issued (in shares)   4,000,000  
Issue price (in dollars per share) | $ / shares   $ 10.00  
Aggregate gross proceeds from issuance | $   $ 40.0  
Net proceeds after deducting underwriting discounts and commissions and estimated offering costs | $   $ 34.0  
Stock split ratio   55.2486  
Number of shares into which convertible preferred stock is converted 7,538,671    
Number of shares issued for each share of convertible preferred stock converted 1    
Convertible preferred stock, outstanding (in shares) 0