Equity (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended
	Jul. 20, 2018	Mar. 31, 2020	Dec. 31, 2019	Aug. 01, 2019
Equity
Common stock, authorized (in shares)	150,000,000	150,000,000	150,000,000
Shares authorized	160,000,000
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001	$ 0.001
Preferred stock, share authorized (in shares)	10,000,000	10,000,000	10,000,000
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001	$ 0.001
Common stock
Equity
Conversion of redeemable convertible preferred stock to common stock (in shares)	51,845,438
IPO
Equity
Shares issued (in shares)	12,055,450
Net proceeds after deducting underwriting discounts and commissions and other offering costs	$ 254.3
IPO | Common stock
Equity
Shares issued (in shares)	12,055,450
Overallotment
Equity
Shares issued (in shares)	1,572,450
At the market offering
Equity
Shares issued (in shares)		0
Percentage of commission				3.00%
Aggregate offering price				$ 100.0