Income Taxes - Summary of Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Current:
Federal	$ 0	$ 0
State	13	0
Current income tax expense (benefit)	13	0
Deferred:
Federal	0	(212)
State	0	(18)
Deferred income tax expense (benefit)	0	(230)
Income tax expense (benefit)	$ 13	$ (230)