GOODWILL AND INTANGIBLE ASSETS - Acquired Intangible Assets (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 237,871	$ 19,846
Accumulated Amortization	(30,548)	(15,551)
Net	$ 207,323	$ 4,295
Weighted Average
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted-Average Useful Life (Years)	4 years 7 months 6 days	9 years
Customer lists
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 128,304	$ 288
Accumulated Amortization	(8,406)	(288)
Net	$ 119,898	0
Customer lists | Weighted Average
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted-Average Useful Life (Years)	4 years 9 months 18 days
Patents and technology
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 101,001	11,044
Accumulated Amortization	(13,893)	(6,943)
Net	$ 87,108	$ 4,101
Patents and technology | Weighted Average
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted-Average Useful Life (Years)	4 years 2 months 12 days	9 years 3 months 18 days
Trade names
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 5,140	$ 5,114
Accumulated Amortization	(4,946)	(5,114)
Net	$ 194	0
Trade names | Weighted Average
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted-Average Useful Life (Years)	1 year 3 months 18 days
Other
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 3,426	3,400
Accumulated Amortization	(3,303)	(3,206)
Net	$ 123	$ 194
Other | Weighted Average
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted-Average Useful Life (Years)	2 years 9 months 18 days	3 years