INTANGIBLE ASSETS AND GOODWILL - Assumption of impairment (Details)	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2016
Goodwill
Estimates and assumptions used for impairment test [Line Items]
Discount rate	8.50%	9.00%	9.00%	9.25%	9.50%
Broadcasting Licenses
Estimates and assumptions used for impairment test [Line Items]
Discount rate	8.50%	9.00%	9.00%	9.25%	9.50%
Broadcasting Licenses | Minimum
Estimates and assumptions used for impairment test [Line Items]
Operating profit margin ranges expected for average stations in the markets where the Company operates	18.00%	22.00%	22.00%	19.00%	14.00%
Forecasted growth rate (including long-term growth rate) range of the Company's markets	0.00%	0.00%	0.50%	1.00%	1.00%
Broadcasting Licenses | Maximum
Estimates and assumptions used for impairment test [Line Items]
Operating profit margin ranges expected for average stations in the markets where the Company operates	36.00%	37.00%	37.00%	40.00%	40.00%
Forecasted growth rate (including long-term growth rate) range of the Company's markets	0.80%	0.90%	1.00%	2.00%	2.00%