Fair Value Measurements - Summary of Changes in Fair Value for the Level 3 Liability (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	$ (1,785)
Unrealized gains/(losses)	94
Ending balance	(1,691)
Equity Warrant Liability
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	(1,471)
Unrealized gains/(losses)	416
Ending balance	(1,055)
Stock Appreciation Rights
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	(314)
Unrealized gains/(losses)	(322)
Ending balance	$ (636)