Consolidated Statements of Comprehensive Loss - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net Loss Attributable to Common Stockholders	$ (8,857,000)	$ (63,509,000)	$ (42,758,000)
Other comprehensive loss, net of tax:
Unrealized loss on short-term investments, net of tax	(17,000)	0	0
Comprehensive Net Loss	$ (8,874,000)	$ (63,509,000)	$ (42,758,000)