Description of Business and Summary of Significant Accounting Policies - Narrative (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2020
Organization Consolidation And Summary Of Significant Accounting Policies [Line Items]
Depreciation and amortization expense		$ 22,826	$ 16,366	$ 14,188
Capitalized computer software		33,900	29,100	11,700
Loss on disposal	$ 5,100	5,147	0	0
Total revenue		366,620	291,609	249,838
Contract acquisition costs		41,000	32,000
Remaining performance obligations		$ 285,700
Percentage of remaining performance obligations to be recognized over next 24 months		90.00%
Revenue from satisfaction of performance obligations and revenue recognized that was included in deferred revenue		$ 103,200
Advertising costs		29,100	28,600	$ 17,400
Allowance for credit losses		5,344	3,070
Accumulated deficit		$ 391,885	$ 283,562
ASU 2016-13 | Accounting standard adoption adjustment
Organization Consolidation And Summary Of Significant Accounting Policies [Line Items]
Allowance for credit losses					$ 700
Accumulated deficit					$ 700
Software and software development costs
Organization Consolidation And Summary Of Significant Accounting Policies [Line Items]
Useful life of assets		5 years
Minimum
Organization Consolidation And Summary Of Significant Accounting Policies [Line Items]
Amortization period for contract acquisition costs (in years)		3 years
Minimum | Stock option
Organization Consolidation And Summary Of Significant Accounting Policies [Line Items]
Requisite service period		3 years
Minimum | Computer equipment and software
Organization Consolidation And Summary Of Significant Accounting Policies [Line Items]
Useful life of assets		3 years
Maximum
Organization Consolidation And Summary Of Significant Accounting Policies [Line Items]
Amortization period for contract acquisition costs (in years)		5 years
Maximum | Stock option
Organization Consolidation And Summary Of Significant Accounting Policies [Line Items]
Requisite service period		4 years
Maximum | Computer equipment and software
Organization Consolidation And Summary Of Significant Accounting Policies [Line Items]
Useful life of assets		5 years