INTANGIBLE ASSETS - Components of Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Schedule of Intangible Assets Disclosure [Line Items]
Goodwill, Gross	$ 30,271		$ 30,271		$ 49,371
Goodwill, Impairment					(19,100)
Goodwill, Net	30,271		30,271		30,271
Finite-lived intangible assets, Accumulated Amortization	(96,997)		(96,997)		(88,106)
Total, Gross	332,759		332,759		352,231
Total, Impairment	0	$ 0	0	$ (20,100)	(20,100)
Total, Net	235,762		235,762		244,025
Licenses
Schedule of Intangible Assets Disclosure [Line Items]
Finite-lived intangible assets, Gross	15,847		15,847		15,847
Finite-lived intangible assets, Accumulated Amortization	(10,970)		(10,970)		(10,742)
Finite-lived intangible assets, Net	4,877		4,877		5,105
Trade names
Schedule of Intangible Assets Disclosure [Line Items]
Finite-lived intangible assets, Gross	52,190		52,190		52,030
Finite-lived intangible assets, Accumulated Amortization	(22,552)		(22,552)		(20,874)
Finite-lived intangible assets, Net	29,638		29,638		31,156
Customer relationships
Schedule of Intangible Assets Disclosure [Line Items]
Finite-lived intangible assets, Gross	178,254		178,254		177,801
Finite-lived intangible assets, Accumulated Amortization	(60,686)		(60,686)		(54,008)
Finite-lived intangible assets, Net	117,568		117,568		123,793
Other
Schedule of Intangible Assets Disclosure [Line Items]
Finite-lived intangible assets, Gross	6,597		6,597		6,582
Finite-lived intangible assets, Accumulated Amortization	(2,789)		(2,789)		(2,482)
Finite-lived intangible assets, Net	3,808		3,808		4,100
Trade names
Schedule of Intangible Assets Disclosure [Line Items]
Indefinite-lived intangible assets, Gross	49,600		49,600		50,600
Indefinite-lived intangible assets, Impairment					(1,000)
Indefinite-lived intangible assets, Net	$ 49,600		$ 49,600		$ 49,600