Fair Value Measurements - Changes in Fair Value of Recurring Measurements (Details) - Derivative Liability Exit Fee [Member] - Other income (expense), net $ in Thousands	6 Months Ended
	Jun. 30, 2019 USD ($)
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	61
Ending Balance	$ 594