UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
OPERATING ACTIVITIES:
Net loss	$ 2,226	$ (30,737)		$ (23,853)	$ (58,761)
Adjustments to reconcile net loss to net cash used in operating activities:
Provision for bad debt			$ 6,300	803	6,445	$ 4,532
DEPRECIATION AND AMORTIZATION	11,471	9,740		33,145	27,084
Amortization of right-of-use asset				5,947
Stock-based compensation expense	2,365	1,149		6,587	3,439
Fair value changes in embedded derivatives				1,651	17,492
FAIR VALUE CHANGES IN BUSINESS ACQUISITIONS CONTINGENT CONSIDERATION		13,404		24,035	17,387
Deferred income taxes				232	(1,563)
Other				68	(1,180)
Debt extinguishment costs				4,052
Changes in operating assets and liabilities—net of acquisitions:
Accounts receivable and contract assets				(12,503)	(7,736)
Prepaid expenses and other current assets				(1,781)	(1,349)
Accounts payable and other accrued liabilities				(3,422)	(4,829)
Accrued payroll and benefits				61	6,084
Payment of contingent consideration and other assumed purchase price obligations				(15,549)	(6,390)
Change in operating leases				(5,765)
Net cash provided by (used in) operating activities				13,708	(3,877)
INVESTING ACTIVITIES:
Purchases of property and equipment				(5,405)	(5,366)
Proprietary software development and other software costs				(241)	(370)
Purchase price true ups				(8,562)
Proceeds from net working capital adjustment related to acquisitions					2,819
Cash paid for acquisitions—net of cash acquired				(36,480)	(173,923)
Net cash used in investing activities				(50,688)	(176,840)
FINANCING ACTIVITIES:
Proceeds from line of credit				109,000	104,390
Payments on line of credit				(72,000)	(201,980)
Proceeds from term loans				175,000	175,000
Repayment of term loan				(173,905)	(49,297)
Payment of contingent consideration and other purchase price obligations				(9,605)	(6,004)
Repayment of finance leases				(1,884)	(2,257)
Proceeds from issuance of common stock in connection with initial public offering, net of issuance costs					161,288
Payments of deferred offering costs					(2,925)
Prepayment premium on credit facility					(351)
Debt issuance costs				(2,590)	(4,866)
Proceeds from issuance of common stock for exercised stock options				6,032	171
Issuance of convertible and redeemable Series A-2 preferred stock and warrant					173,664
Redemption of the Series A-1 preferred stock					(131,821)
Dividend payment to the Series A-2 shareholders				(12,300)	(2,870)
Exercise of warrant options					25
Net cash provided by financing activities				17,748	212,167
CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH				(19,232)	31,450
Foreign exchange impact on cash balance				357	43
Beginning of year			$ 6,884	34,881	6,884	6,884
End of period	$ 16,006	$ 38,377		16,006	38,377	$ 34,881
SUPPLEMENTAL DISCLOSURES OF CASH FLOWS INFORMATION:
Cash paid for interest				4,649	9,368
Cash paid for income tax				958	171
SUPPLEMENTAL DISCLOSURES OF NON-CASH INVESTING AND FINANCING ACTIVITIES:
Series A-1 preferred stock deemed dividends—net of return from holders					24,341
Series A-1 preferred stock dividend paid in common shares					26,801
Accrued purchases of property and equipment				1,171	486
Property and equipment purchased under finance leases				1,766	1,753
Accretion of the redeemable series A-1 preferred stock to redeemable value					17,601
Common stock issued to acquire new businesses				6,020	25,000
Acquisitions unpaid contingent consideration				35,352	58,912
Offering costs included in accounts payable and other accrued liabilities				389	$ 1,237
Acquisitions contingent consideration and purchase price true ups paid in shares				$ 26,084