Summary of Significant Accounting Policies - Additional information (Detail) $ in Thousands		9 Months Ended	12 Months Ended
	Sep. 10, 2021 shares	Sep. 30, 2021 USD ($) Segment shares	Dec. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)
Stockholders' equity note, stock split	1,198-for-1	1,198-for-1
Stock holder equity split shares issued | shares	1,198	1,198
Number of operating segments | Segment		1
Cash and cash equivalents		$ 192,397	$ 66,633	$ 57,458	$ 50,299
Foreign currency transaction gain (loss), before tax		$ 900	100
Percentage revenue processed		95.00%
Outside US [Member]
Cash		$ 42,800	29,400
India [Member]
Cash		12,800	10,300
Canada [Member]
Cash		$ 14,100	$ 7,000
Internally Developed Software Assets [Member]
Estimated useful lives		3 years