Goodwill and Intangible Assets - Schedule of Amounts Related to Finite-Lived Intangible Assets (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Gross Balance	$ 279,578	$ 250,148
Accumulated Amortization	119,339	95,294
Total Intangible Assets—Net	160,239	154,854
Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Gross Balance	189,103	164,782
Accumulated Amortization	67,328	53,446
Total Intangible Assets—Net	$ 121,775	$ 111,336
Customer Relationships | Minimum
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life	2 years	7 years
Customer Relationships | Maximum
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life	15 years	15 years
Covenants Not to Compete
Finite-Lived Intangible Assets [Line Items]
Gross Balance	$ 31,623	$ 29,942
Accumulated Amortization	24,832	21,469
Total Intangible Assets—Net	$ 6,791	$ 8,473
Covenants Not to Compete | Minimum
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life	4 years	4 years
Covenants Not to Compete | Maximum
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life	5 years	5 years
Trade Names
Finite-Lived Intangible Assets [Line Items]
Gross Balance	$ 19,778	$ 16,938
Accumulated Amortization	15,107	12,849
Total Intangible Assets—Net	$ 4,671	$ 4,089
Trade Names | Minimum
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life	1 year	1 year
Trade Names | Maximum
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life	5 years	5 years
Proprietary Software
Finite-Lived Intangible Assets [Line Items]
Gross Balance	$ 21,595	$ 21,007
Accumulated Amortization	9,853	6,132
Total Intangible Assets—Net	$ 11,742	$ 14,875
Proprietary Software | Minimum
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life	3 years	3 years
Proprietary Software | Maximum
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life	5 years	5 years
Patent
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life	16 years	16 years
Gross Balance	$ 17,479	$ 17,479
Accumulated Amortization	2,219	1,398
Total Intangible Assets—Net	$ 15,260	$ 16,081