Stock Incentive Plans - Employee Stock Purchase Plan (Narrative) (Details) $ in Thousands		3 Months Ended
	Jun. 21, 2016 shares	Mar. 31, 2020 USD ($) offering_period shares	Mar. 31, 2019 USD ($) shares	Dec. 31, 2019 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock authorized and reserved for future issuance (in shares)		44,390,813		40,169,185
Stock-based compensation expense | $		$ 1,409	$ 1,180
ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of offering periods under the ESPP | offering_period		2
Eligible compensation withheld for use (up to) (as a percent)	25.00%
Purchase price of shares (not less than) (as a percent)	85.00%
Common stock authorized and reserved for future issuance (in shares)	173,076	1,532,077
Number of shares of common stock outstanding (as a percent)	0.01
Number of shares authorized, increase (in shares)		863,254	224,717
Shares of common stock issued to employees under the ESPP (in shares)		78,583
Stock-based compensation expense | $		$ 100	$ 100