Business Combinations - Acquisitions (Details) $ in Thousands					3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 09, 2021 USD ($)	May 20, 2021 USD ($)	Apr. 05, 2021 USD ($)	Jan. 12, 2021 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) item	Sep. 30, 2020 USD ($)	Dec. 31, 2020
Business Combinations
Contingent consideration					$ 624		$ 624
Unaudited Pro Forma Consolidated Financial Information
Revenue					62,769	$ 40,762	160,379	$ 109,599
Net loss					(5,099)	$ (41,820)	(84,516)	$ (69,428)
General and administrative
Business Combinations
Acquisition related costs							5,400
January 12, 2021 Acquisition ("V12 Data")
Business Combinations
Cash paid in business acquisition				$ 20,346
Total consideration				21,756
Contingent consideration				$ 1,400
Contingent consideration earnout period				2 years
Net assets acquired				$ 21,756
Estimated fair value				$ 1,410
Estimated Useful Life (in years)				7 years 7 months 6 days
Fair value of the intangible assets as of the date of the acquisition
Fair Value				$ 6,440
January 12, 2021 Acquisition ("V12 Data") | General and administrative
Business Combinations
Acquisition related costs							274
April 5, 2021 Acquisition ("HOA")
Business Combinations
Cash paid in business acquisition			$ 82,355
Total consideration			113,741
Issuance of common stock			21,687
Net assets acquired			113,741
Acquisition hold backs			$ 9,700
Consideration transferred, working capital adjustment					300
Estimated Useful Life (in years)			9 years 6 months
April 5, 2021 Acquisition ("HOA") | General and administrative
Business Combinations
Acquisition related costs							2,900
May 20, 2021 Acquisition ("Rynoh")
Business Combinations
Cash paid in business acquisition		$ 32,302
Total consideration		35,802
Net assets acquired		35,802
Acquisition hold backs		$ 3,500
Estimated Useful Life (in years)		10 years
May 20, 2021 Acquisition ("Rynoh") | General and administrative
Business Combinations
Acquisition related costs							1,600
September 9, 2021 Acquisition ("AHP")
Business Combinations
Cash paid in business acquisition	$ 43,750
Total consideration	46,250
Net assets acquired	46,250
Acquisition hold backs	$ 2,500
Estimated Useful Life (in years)	7 years
September 9, 2021 Acquisition ("AHP") | General and administrative
Business Combinations
Acquisition related costs							300
Other Acquisitions
Business Combinations
Cash paid in business acquisition							25,321
Total consideration							28,754
Issuance of common stock							3,106
Net assets acquired					28,754		28,754
Estimated fair value							327
Goodwill to be not deductible for income tax purposes					3,600		3,600
Goodwill to be deductible for income tax purposes					10,000		10,000
Other Acquisitions | General and administrative
Business Combinations
Acquisition related costs							300
Total Acquisition
Business Combinations
Cash paid in business acquisition							204,074
Total consideration							246,303
Issuance of common stock							24,793
Net assets acquired					$ 246,303		246,303
Estimated fair value							$ 1,737
Number of acquisitions | item							4
Revenue							$ 55,300
Net income							$ 1,200
Customer relationships
Business Combinations
Estimated Useful Life (in years)							10 years
Fair value of the intangible assets as of the date of the acquisition
Estimated Useful Life (in years)							9 years		7 years
Customer relationships | January 12, 2021 Acquisition ("V12 Data")
Fair value of the intangible assets as of the date of the acquisition
Fair Value				$ 1,650
Estimated Useful Life (in years)				10 years
Customer relationships | April 5, 2021 Acquisition ("HOA")
Business Combinations
Estimated Useful Life (in years)			10 years
Customer relationships | May 20, 2021 Acquisition ("Rynoh")
Business Combinations
Estimated Useful Life (in years)		10 years
Acquired technology
Business Combinations
Estimated Useful Life (in years)							5 years
Fair value of the intangible assets as of the date of the acquisition
Estimated Useful Life (in years)							6 years		6 years
Acquired technology | January 12, 2021 Acquisition ("V12 Data")
Fair value of the intangible assets as of the date of the acquisition
Fair Value				$ 3,525
Estimated Useful Life (in years)				4 years
Acquired technology | May 20, 2021 Acquisition ("Rynoh")
Business Combinations
Estimated Useful Life (in years)		7 years
Trademarks and tradenames
Business Combinations
Estimated Useful Life (in years)							11 years
Fair value of the intangible assets as of the date of the acquisition
Estimated Useful Life (in years)							9 years		9 years
Trademarks and tradenames | January 12, 2021 Acquisition ("V12 Data")
Fair value of the intangible assets as of the date of the acquisition
Fair Value				$ 1,225
Estimated Useful Life (in years)				15 years
Trademarks and tradenames | April 5, 2021 Acquisition ("HOA")
Business Combinations
Estimated Useful Life (in years)			10 years
Trademarks and tradenames | May 20, 2021 Acquisition ("Rynoh")
Business Combinations
Estimated Useful Life (in years)		20 years
Trademarks and tradenames | September 9, 2021 Acquisition ("AHP")
Business Combinations
Estimated Useful Life (in years)	10 years
Non-competition agreements
Business Combinations
Estimated Useful Life (in years)							2 years
Fair value of the intangible assets as of the date of the acquisition
Estimated Useful Life (in years)							2 years		2 years
Non-competition agreements | January 12, 2021 Acquisition ("V12 Data")
Fair value of the intangible assets as of the date of the acquisition
Fair Value				$ 40
Estimated Useful Life (in years)				2 years
Non-competition agreements | May 20, 2021 Acquisition ("Rynoh")
Business Combinations
Estimated Useful Life (in years)		1 year