Summary of significant accounting policies - Stock-Based Compensation (Details) - USD ($) $ in Thousands		3 Months Ended	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2021	Jun. 30, 2021
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	$ 19,400	$ 19,433	$ 19,433
Sales and marketing
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation		3,826	3,826
Product development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation		1,994	1,994
General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation		$ 13,613	$ 13,613