Stock-Based Compensation - Employee Stock Purchase Plan (Details) - Employee Stock Purchase Plan - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 131	$ 1,033	$ 850
Common stock purchased by Company employees	103,981	60,695.3	44,649
Average purchase price per share (USD per share)	$ 3.33	$ 22.16	$ 56.43