Stock-Based Compensation - Employee Stock Purchase Plan (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Jan. 01, 2019
Stock Options
Issuance of common stock for employee stock purchase plan	$ 1,059	$ 637
Total stock-based compensation	$ 2,903	1,389	$ 5,652	$ 2,780
Employee Stock Purchase Plan
Stock Options
Employee stock purchase plan, percent			85.00%
Number of shares reserved for issuance (in shares)	598,698		598,698		277,362
Number of additional shares reserved for issuance, maximum (in shares)					184,908
Number of additional shares reserved for issuance, percentage, maximum					1.00%
Issuance of common stock for employee stock purchase plan (in shares)			16,730
Issuance of common stock for employee stock purchase plan			$ 1,100
Total stock-based compensation	$ 200	$ 100	$ 300	$ 200