Property and Equipment - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Depreciation	$ 322	$ 16	$ 591	$ 172
Accumulated depreciation	1,724		1,724		$ 1,151
Inventory
Property, Plant and Equipment [Line Items]
Accumulated depreciation	76		76
Prepaid expenses and other assets
Property, Plant and Equipment [Line Items]
Accumulated depreciation	$ 42		$ 42