Warrants (Tables)

12 Months Ended

Dec. 31, 2018

Warrants [Abstract]

Warrant Liability

A roll-forward of warrant liability is as follows:

Balance as of December 31, 2016	$	6,550
Changes in fair value recognized		1,123
Balance as of December 31, 2017		7,673
Changes in fair value recognized		5,278
Exercise of warrants		(12,951	)
Balance as of December 31, 2018	$	—