Stockholders' Equity - Allocation Of Proceeds (Details) - Interstate Battery System International, Inc. and Other Investors $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($)
Class of Stock [Line Items]
Fair value	$ 26,463
Allocated value	10,000
Convertible Note
Class of Stock [Line Items]
Fair value	4,879
Allocated value	1,844
Warrant
Class of Stock [Line Items]
Fair value	13,586
Allocated value	5,134
Common Stock
Class of Stock [Line Items]
Fair value	7,998
Allocated value	$ 3,022