Fair Value Measurements - Summary of Changes in Fair Value for the Level 3 Liability (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($)
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance	$ (1,785)
Unrealized losses	(280)
Ending balance	(2,065)
Warrant
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance	(1,471)
Unrealized losses	(152)
Ending balance	(1,623)
Deferred Compensation
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance	(314)
Unrealized losses	(128)
Ending balance	$ (442)