Nature of Business and Basis of Presentation - Additional Information (Details) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended						9 Months Ended
	Jan. 31, 2021 USD ($) $ / shares shares	Sep. 30, 2021 USD ($) Subsidiary	Jun. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Sep. 30, 2021 USD ($) Subsidiary	Sep. 30, 2020 USD ($)		Dec. 31, 2020 USD ($) Subsidiary		Dec. 31, 2019 USD ($)
Nature Of Business And Basis Of Presentation [Line Items]
Number of development subsidiaries | Subsidiary		5						5			5
Proceeds from initial public offering	$ 264,500							$ 267,268
Reverse stock split conversion ratio								1
Reverse stock split								one-for-7.0390
Net Income (loss)		$ 18,259	$ 16,439	$ (1,419)	$ 11,314	$ 13,875	$ 5,163	$ 33,279	$ 30,352	[1]
Accumulated deficit		(126,395)			$ (64,993)			(126,395)	$ (64,993)		$ (93,339)	[2]	$ (41,540)
Cash, cash equivalents, short-term investments and long-term investments		$ 445,400						$ 445,400
IPO
Nature Of Business And Basis Of Presentation [Line Items]
Common stock shares issued and sold | shares	13,685,000
Stock, price per Share | $ / shares	$ 21.00
Underwriters' Option
Nature Of Business And Basis Of Presentation [Line Items]
Common stock shares issued and sold | shares	1,785,000

[1] The shares and per share amounts for the nine months ended September 30, 2020 were derived from the unaudited consolidated financial statements as of that date and were retroactively adjusted as a result of the Reorganization and Reverse Stock Split. See Note 3 to the unaudited consolidated financial statements for additional details.

[2] The consolidated balance sheet as of December 31, 2020 is derived from the audited consolidated financial statements as of that date and was retroactively adjusted, including shares and per share amounts, as a result of the Reorganization and Reverse Stock Split. See Note 3 to the unaudited consolidated financial statements for additional details.