Annual report pursuant to Section 13 and 15(d)

Stockholders' Equity - Fair Value of Warrants in Investment Agreement Using the Black-Scholes-Merton Option (Details)

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Stockholders' Equity - Fair Value of Warrants in Investment Agreement Using the Black-Scholes-Merton Option (Details) - USD ($)
$ / shares in Units, $ in Thousands
12 Months Ended
Jun. 24, 2018
Dec. 31, 2019
May 24, 2016
Class of Stock [Line Items]      
Warrant shares issued (in shares)   807,436  
Market price     $ 11.39
Warrant 1 | Interstate Battery System International, Inc.      
Class of Stock [Line Items]      
Warrant shares issued (in shares)   702,247  
Market price   $ 11.39  
Warrant exercise price (in dollars per share)   $ 7.12  
Term   2 years  
Risk free interest rate   0.91%  
Volatility 80.20% 65.70%  
Dividend rate 0.00% 0.00%  
Per share FV of warrant (in usd per share)   $ 5.89  
FV of warrant   $ 4,136  
Warrant 2 | Interstate Battery System International, Inc.      
Class of Stock [Line Items]      
Warrant shares issued (in shares)   1,605,131  
Market price   $ 11.39  
Warrant exercise price (in dollars per share)   $ 9.00  
Term   3 years  
Risk free interest rate   1.05%  
Volatility   67.80%  
Dividend rate   0.00%  
Per share FV of warrant (in usd per share)   $ 5.89  
FV of warrant   $ 9,450