Stock-based Compensation - Employee Stock Purchase Plan (Details) $ in Thousands	1 Months Ended	3 Months Ended		12 Months Ended
	Jan. 31, 2020 shares	Mar. 31, 2020 USD ($) item shares	Mar. 31, 2019 USD ($)	Dec. 31, 2019 shares	Dec. 31, 2018 shares
Stock-based compensation
Stock-based compensation expense | $		$ 2,584	$ 2,738
2017 Employee Stock Purchase Plan
Stock-based compensation
Shares Authorized					223,341
Employee basic pay holding period		6 months
Number of offering periods | item		2
Percentage of market value at which employee may purchase stock		85.00%
Issuance under employee stock purchase plan (in shares)	85,553			123,664
2017 Employee Stock Purchase Plan | Maximum
Stock-based compensation
Shares Authorized		893,441
Threshold percentage of share available to grant		1.00%