FAIR VALUE MEASUREMENTS (Tables)
 12 Months Ended
Dec. 31, 2019
Fair Value Disclosures [Abstract]  
Summary of Quantitative Inputs
The following table presents the quantitative inputs, which we classify in Level 3 of the fair value hierarchy, used in estimating the fair value of the warrants:
 
December 31,
 
2019
 
2018
CBG Financing Warrants
 
 
 
Expected volatility
85.00
%
 
70.00
%
Risk-free interest rate
1.60
%
 
2.52
%
Expected remaining term (years)
0.73

 
1.73

CBG Acquisition Warrants
 
 
 
Expected volatility
75.00
%
 
70.00
%
Risk-free interest rate
1.65
%
 
2.46
%
Expected remaining term (years)
3.72

 
4.72


If we added or subtracted five percentage points with regard to our estimate of expected volatility, or if our stock price increased or decreased by five percent, our estimates of fair value would not materially change
Summary of Change in Liability Balance Associated with Liability-Classified Warrants
The following table presents the change in the liability balance associated with our liability-classified warrants (in thousands):
 
Year Ended December 31,
 
2019
 
2018
Balance at beginning of period
$
1,383

 
$
89,169

Warrant exercises
—

 
(59,907
)
Increase (decrease) in fair value
(1,268
)
 
(27,879
)
Balance at end of period
$
115

 
$
1,383
Summary of Change in Balance of Liability Associated with Earnout Payments
The following table presents the change during the years ended December 31, 2019 and 2018 in the balance of the liability associated with the Earnout Payments (in thousands):
 
December 31,
 
2019
 
2018
Balance at beginning of period
$
990

 
$
1,930

Payments
(8
)
 
(1,000
)
Change in fair value of contingent consideration
10

 
60

Interest accrued on unpaid balance
94

 
—

Balance at end of period
$
1,086

 
$
990