INTANGIBLE ASSETS AND GOODWILL - Assumption of impairment (Details)	3 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019	Dec. 31, 2018	Jun. 30, 2018
Goodwill
Estimates and assumptions used for impairment test [Line Items]
Discount rate				8.50%	9.00%	9.00%
Broadcasting Licenses
Estimates and assumptions used for impairment test [Line Items]
Discount rate	8.50%	7.50%	8.00%	8.50%	9.00%	9.00%
Broadcasting Licenses | Minimum
Estimates and assumptions used for impairment test [Line Items]
Operating profit margin ranges for average stations in markets where the Company operates	20.00%	24.00%	22.00%	18.00%	22.00%	22.00%
Forecasted growth rate (including long-term growth rate) range of the Company's markets	0.00%	0.00%	0.00%	0.00%	0.00%	0.50%
Broadcasting Licenses | Maximum
Estimates and assumptions used for impairment test [Line Items]
Operating profit margin ranges for average stations in markets where the Company operates	36.00%	36.00%	36.00%	36.00%	37.00%	37.00%
Forecasted growth rate (including long-term growth rate) range of the Company's markets	0.60%	0.70%	0.80%	0.80%	0.90%	1.00%