Stock-Based Compensation - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended			60 Months Ended
	Jan. 31, 2019	Dec. 31, 2018	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2019
Stock-Based Compensation
Shares issued under the Employee Stock Purchase Plan (in shares)				$ 932	$ 656	$ 425
Granted (in shares)				2,033,760
Expected to vest (in shares)				4,700,318			4,700,318
Total unrecognized compensation cost				$ 16,600			$ 16,600
Intrinsic value of stock options exercised				$ 12,400	10,300	700
Service-based stock options
Stock-Based Compensation
Expiration period				10 years
Vesting period				4 years
Stock-based compensation expense				$ 11,800	$ 6,900	$ 2,500
Granted (in shares)				2,033,760
Weighted average grant-date fair value (in dollars per share)				$ 12.62	$ 6.96	$ 1.99
Weighted average period over which unrecognized compensation is expected to be recognized				3 years 2 months 12 days
Employee stock
Stock-Based Compensation
Common stock available for issuance (in shares)				1,000,000			1,000,000
Common stock granted since inception (in shares)							595,799
Shares purchased during period (in shares)	19,076
Shares issued under the Employee Stock Purchase Plan (in shares)		$ 200
Stock-based compensation expense				$ 300	$ 300	$ 200
Restricted Stock Units (RSUs)
Stock-Based Compensation
Vesting period				4 years
Stock-based compensation expense				$ 1,000
Unrecognized compensation cost				$ 1,800			$ 1,800
Weighted average period over which unrecognized compensation is expected to be recognized				3 years 1 month 6 days
Grant-date fair value of restricted stock units granted				$ 3,310
Restricted stock units granted (shares)				186,922	0
Prior Plans
Stock-Based Compensation
Awards available for future grant under the Plan (in shares)				0			0
Omnibus Incentive Plan 2019
Stock-Based Compensation
Awards available for future grant under the Plan (in shares)				3,344,242			3,344,242
Nonemployee directors | Service-based stock options
Stock-Based Compensation
Expiration period				10 years
Vesting period			1 year	1 year
Granted (in shares)				78,750