Income Taxes - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Tax Credit Carryforward [Line Items]
Remeasurement of deferred tax assets		$ 10,800
Net operating loss carryforwards	$ 97,900
Aggregate limitation on utilization of certain net operating losses and credits	4,600
Tax credit write off	2,800
Gross deferred tax assets	$ (33,136)	$ (22,509)
Valuation allowance percent	100.00%	100.00%
Increase (decrease) in valuation allowance	$ (10,600)	$ 3,800
Research and experimentation tax carryforward
Tax Credit Carryforward [Line Items]
Tax credit carryforward amount	$ 6,600