Acquisitions of Businesses - Summary of Reconciliation of Preliminary Total Consideration (Details) $ in Thousands, € in Millions										3 Months Ended			6 Months Ended	12 Months Ended
	Oct. 18, 2021 USD ($)	Oct. 01, 2021 USD ($)	Jun. 30, 2021 USD ($)	Apr. 20, 2021 USD ($)	Apr. 01, 2021 USD ($)	Apr. 01, 2021 EUR (€)	Dec. 31, 2020 USD ($)	Nov. 05, 2020 USD ($)	Oct. 05, 2020 USD ($)	Sep. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Business Acquisition [Line Items]
Accrued value of earnout related to acquisition							$ 34,468					$ 34,468	$ 67,280	$ 67,280	$ 34,468	$ 15,351
Inposia
Business Acquisition [Line Items]
Consideration in cash			$ 14,671		$ 12,200					$ 14,500		2,400	14,456
Fair value of common stock issued at closing			22,971										22,971
Total consideration			37,642		$ 37,400	€ 31.8							37,427
Inposia | Restatement Adjustment
Business Acquisition [Line Items]
Consideration in cash													(215)
Total consideration													(215)
Davo Technologies LLC
Business Acquisition [Line Items]
Consideration in cash			23,818	$ 23,500							$ 300		23,818
Acquisition holdbacks with a fair value upon acquisition			2,600	2,600									2,591	2,591
Accrued value of earnout related to acquisition			28,620	30,300									30,338	30,338
Total consideration			$ 55,038	$ 56,700									56,747
Davo Technologies LLC | Restatement Adjustment
Business Acquisition [Line Items]
Acquisition holdbacks with a fair value upon acquisition													(9)	(9)
Accrued value of earnout related to acquisition													1,718	1,718
Total consideration													1,709
Track1099 LLC
Business Acquisition [Line Items]
Consideration in cash		$ 35,000												35,000
Acquisition holdbacks with a fair value upon acquisition		5,000											4,984	4,984
Accrued value of earnout related to acquisition		8,800											8,820	8,820
Total consideration		$ 48,800												48,804
CrowdReason LLC and CorrelationAdvisors
Business Acquisition [Line Items]
Consideration in cash	$ 8,300													8,317
Acquisition holdbacks with a fair value upon acquisition	1,700												1,727	1,727
Accrued value of earnout related to acquisition	26,300												26,320	26,320
Total consideration	$ 36,400													36,364
Transaction Tax Resources, Inc.
Business Acquisition [Line Items]
Consideration in cash							294,017		$ 294,000					294,017
Acquisition holdbacks with a fair value upon acquisition							57,477		57,300			57,477	57,260	57,260	57,477
Accrued value of earnout related to acquisition							15,740		18,900			15,740	18,871	18,871	15,740
Total consideration							367,234		$ 370,100					370,148
Transaction Tax Resources, Inc. | Restatement Adjustment
Business Acquisition [Line Items]
Acquisition holdbacks with a fair value upon acquisition													(217)	(217)
Accrued value of earnout related to acquisition													3,131	3,131
Total consideration														2,914
Business Licenses
Business Acquisition [Line Items]
Consideration in cash								$ 64,800						64,812	64,812
Acquisition holdbacks with a fair value upon acquisition							11,415	11,100				11,415	11,109	11,109	11,415
Accrued value of earnout related to acquisition							$ 18,728	17,400				$ 18,728	17,400	17,400	18,728
Total consideration								$ 93,300						93,321	$ 94,955
Business Licenses | Restatement Adjustment
Business Acquisition [Line Items]
Acquisition holdbacks with a fair value upon acquisition													(306)	(306)
Accrued value of earnout related to acquisition													$ (1,328)	(1,328)
Total consideration														$ (1,634)