Stock-Based Compensation - Stock options activity (Details) - Stock Options - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended	12 Months Ended
	Apr. 16, 2019	Mar. 31, 2020	Dec. 31, 2019
Common stock reserved for future issuance
Expiry period	10 years
Number of shares
Outstanding at beginning of period (in shares)		1,046,373
Options granted (in shares)		5,722
Outstanding at end of period (in shares)		1,052,095	1,046,373
Weighted-average exercise price
Outstanding price at beginning (per share)		$ 17.05
Options granted (per share)		55.59
Outstanding price at ending (per share)		$ 17.26	$ 17.05
Additional disclosures
Weighted average remaining contractual term for outstanding options (in years)		9 years 29 days	9 years 3 months 29 days
Aggregate intrinsic value		$ 43,030	$ 35,039
Total unrecognized stock-based compensation expense		$ 2,900
Weighted-average period over which unrecognized stock-based compensation expense is expected to be recognized		2 years 11 days
Minimum
Common stock reserved for future issuance
Vesting period	2 years
Vesting percentage on the first anniversary of the grant date	25.00%
Maximum
Common stock reserved for future issuance
Vesting period	4 years
Vesting percentage on the first anniversary of the grant date	50.00%
2019 Equity Incentive Plan
Number of shares
Outstanding at end of period (in shares)		1,052,095