Fair Value Measurements - Changes in Fair Value of Recurring Measurements (Details) - Derivative Liability Exit Fee [Member] - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	May 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Beginning Balance		$ 533
Change in estimated fair value of derivative liability for exit fee	$ 546	436	$ (13)
Ending Balance		$ 969	$ 533