ORGANIZATION AND BASIS OF PRESENTATION - Contract with Customers (Details) $ in Thousands	6 Months Ended
	Mar. 31, 2021 USD ($) type	Sep. 30, 2020 USD ($)
Revenue from External Customer [Line Items]
Contract assets	$ 132,000	$ 129,200
Number of types of liabilities | type	3
Contract related liabilities	$ 65,993	60,331
Mohegan Sun Pocono
Revenue from External Customer [Line Items]
Contract related liabilities	16,200	16,800
Outstanding gaming chips and slot tickets liability
Revenue from External Customer [Line Items]
Contract related liabilities	9,104	7,623
Loyalty points deferred revenue liability
Revenue from External Customer [Line Items]
Contract related liabilities	37,333	35,368
Patron advances and other liability
Revenue from External Customer [Line Items]
Contract related liabilities	$ 19,556	$ 17,340