ORGANIZATION AND BASIS OF PRESENTATION - Contract with Customers (Details) $ in Thousands	9 Months Ended
	Jun. 30, 2021 USD ($) type	Sep. 30, 2020 USD ($)
Revenue from External Customer [Line Items]
Contract assets	$ 98,600	$ 129,200
Number of types of liabilities | type	3
Contract related liabilities	$ 75,366	60,331
Mohegan Sun Pocono
Revenue from External Customer [Line Items]
Contract related liabilities	15,900	16,800
Outstanding gaming chips and slot tickets liability
Revenue from External Customer [Line Items]
Contract related liabilities	8,576	7,623
Loyalty points deferred revenue liability
Revenue from External Customer [Line Items]
Contract related liabilities	40,095	35,368
Patron advances and other liability
Revenue from External Customer [Line Items]
Contract related liabilities	$ 26,695	$ 17,340