FAIR VALUE MEASUREMENTS - Additional Information (Details)	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017	Dec. 15, 2016	Oct. 13, 2015
Senior Notes – 6.000%
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate (percent)	6.00%				6.00%
Senior Notes | Senior Notes – 5.250%
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate (percent)	5.25%	5.25%	5.25%	5.25%
Senior Notes | Senior Notes – 6.000%
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate (percent)	6.00%	6.00%