Basis of Presentation and Summary of Significant Accounting Policies - Supplemental Schedule of Noncash Investing and Financing Activities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Supplemental Schedule of Non-Cash Investing and Financing Activities
Accrued purchases of property, equipment, and software	$ 1,141	$ 2,195	$ 2,728
Series A preferred stock conversion	100,000	0	0
Series A preferred stock accretion, net	17,567	3,532	3,244
Vendor financed insurance premiums	$ 0	$ 1,450	$ 2,082