SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Additional Information Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accounting Policies [Abstract]
Payments of Financing Costs	$ 0	$ 847	$ 2,433
Asset impairment charge	4,152	1,470	0
Depreciation	12,100	11,600	10,800
Unamortized debt issuance costs	$ 2,700	3,500
Unamortized debt issuance costs, weighted average amortization period, years	3 years 1 month 6 days
Deferred tax assets	$ 47,987	21,427
Non-cash compensation	26,730	25,040	17,887
Share-based compensation, tax benefit recognized	4,700	4,600	4,300
Advertising expense	8,000	8,500	$ 7,000
Finite-Lived Intangible Assets [Line Items]
Non-cash impairment charge for write-off of intangible assets	4,200	1,500
Acquired Names [Member]
Finite-Lived Intangible Assets [Line Items]
Non-cash impairment charge for write-off of intangible assets	4,200	1,500
Noncompete Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Non-cash impairment charge for write-off of intangible assets	$ 0	$ 0
Noncompete Agreements [Member] | Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated useful life of intangible assets	2 years
Noncompete Agreements [Member] | Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated useful life of intangible assets	3 years
Acquired Names [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated useful life of intangible assets	3 years