Common Stock - Additional Information (Details) $ / shares in Units, $ in Thousands									1 Months Ended			3 Months Ended	12 Months Ended
	Feb. 25, 2020 USD ($) $ / shares shares	Feb. 19, 2020 USD ($) $ / shares shares	Sep. 03, 2019 USD ($) $ / shares shares	Aug. 19, 2019 USD ($) $ / shares shares	Jun. 20, 2018 USD ($) $ / shares shares	Jun. 11, 2018 USD ($) $ / shares shares	Oct. 04, 2017 USD ($) $ / shares shares	Oct. 02, 2017 USD ($) $ / shares shares	Feb. 29, 2020 USD ($) $ / shares shares	Jun. 30, 2018 USD ($) $ / shares shares	Oct. 31, 2017 USD ($) $ / shares shares	Sep. 30, 2019 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($) shares	Dec. 31, 2017 USD ($) shares
Class of Stock [Line Items]
Share conversion ratio								5.65
Conversion of preferred stock to common stock (in shares)											24,425,190
Proceeds from additional offering of shares | $													$ 432,400	$ 185,933	$ 129,112
Common Shares
Class of Stock [Line Items]
Number of additional shares issued and sold (in shares)													12,432,431	4,945,000	8,166,496
IPO
Class of Stock [Line Items]
Number of additional shares issued and sold (in shares)								7,500,000			8,166,496
Additional offering price of common stock (in dollars per share) | $ / shares											$ 17.00
Net proceeds from initial public offering | $								$ 114,100			$ 124,600
IPO | Common Shares
Class of Stock [Line Items]
Conversion of preferred stock to common stock (in shares)								24,425,190
Additional offering price of common stock (in dollars per share) | $ / shares								$ 17.00
Over-Allotment Option
Class of Stock [Line Items]
Number of additional shares issued and sold (in shares)							666,496
Proceeds from additional offering of shares | $							$ 10,500
Over-Allotment Option | Common Shares
Class of Stock [Line Items]
Additional offering price of common stock (in dollars per share) | $ / shares							$ 17.00
Follow On Offering | Common Shares
Class of Stock [Line Items]
Number of additional shares issued and sold (in shares)			1,621,621	10,810,810	645,000	4,300,000				4,945,000		12,432,431
Additional offering price of common stock (in dollars per share) | $ / shares			$ 37.00	$ 37.00	$ 40.00	$ 40.00				$ 40.00		$ 37.00
Net proceeds from initial public offering | $			$ 56,400	$ 375,400	$ 24,300	$ 161,000				$ 185,300		$ 431,800
Follow On Offering | Common Shares | Subsequent Event
Class of Stock [Line Items]
Number of additional shares issued and sold (in shares)	477,272	3,181,818							3,659,090
Additional offering price of common stock (in dollars per share) | $ / shares	$ 55.00	$ 55.00							$ 55.00
Net proceeds from initial public offering | $	$ 24,700	$ 163,700							$ 188,400