COMMITMENTS AND CONTINGENCIES (Details)		3 Months Ended		9 Months Ended
	Aug. 12, 2016	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($) gaming_facility slot_machine	Jun. 30, 2015 USD ($)	Sep. 30, 2015 USD ($)
Slot Win Contributions
Commitments and Contingencies [Line Items]
Contribution frequency period				12 months
Contribution determination criteria 1, percent of gross revenues from slot machines, lesser of				30.00%
Contribution determination criteria 2a, lesser of, percent of gross revenues from slot machines, greater of				25.00%
Contribution determination criteria 2b, lesser of, set cash contribution				$ 80,000,000.0
Contribution rate applied to excess free promotional play revenues in excess of limitation, if other than standard rate				25.00%
Limitation of excluded free promotional play as a percent of gross revenues from slot machines				11.00%
Slot win contributions		$ 37,000,000	$ 37,000,000	$ 109,600,000	$ 107,800,000
Slot win contributions outstanding		11,400,000		$ 11,400,000		$ 11,900,000
Pennsylvania Slot Machine Tax
Commitments and Contingencies [Line Items]
Tax rate applied to percent of gross revenues from slot machines				55.00%
Portion of taxed revenues subject to minimum annual local share assessment				2.00%
Minimum annual local share assessment				$ 10,000,000.0
Escrow deposit for tax payments		1,500,000		1,500,000
Slot machine tax expense recognized		31,100,000	31,100,000	91,800,000	88,700,000
Slot machine tax expense, outstanding		3,400,000		$ 3,400,000		4,700,000
Pennsylvania Slot Machine Tax | Downs Racing, L.P.
Commitments and Contingencies [Line Items]
Number of slot machines at Mohegan Sun at Pocono permitted by license | slot_machine				3,000
Permitted slot machine capacity (in slot machines) | slot_machine				5,000
Pennsylvania Table Game Tax
Commitments and Contingencies [Line Items]
Initial tax rate				12.00%
Additional local tax				2.00%
Table game tax expense recognized		1,600,000	1,800,000	$ 4,700,000	5,200,000
Table game tax expense outstanding		157,000		$ 157,000		148,000
Pennsylvania Table Game Tax | Subsequent Event
Commitments and Contingencies [Line Items]
Initial tax rate	14.00%
Additional local tax	2.00%
Pennsylvania Regulatory Fee
Commitments and Contingencies [Line Items]
Fee rate, percent of gross revenues from slot machines and table games				1.50%
Regulatory fee recognized		1,200,000	1,200,000	$ 3,500,000	3,400,000
Regulatory fee outstanding		94,000		94,000		70,000
Pennsylvania Regulatory Fee | Subsequent Event
Commitments and Contingencies [Line Items]
Fee rate, percent of gross revenues from slot machines and table games	1.70%
Pennsylvania Gaming Control Board Loans
Commitments and Contingencies [Line Items]
Loans granted by PGCB				36,100,000
Additional Loans granted by PGCB				$ 63,800,000
Number of authorized gaming facilities | gaming_facility				14
Number of authorized gaming facilities that have commenced operations | gaming_facility				12
PGCB loan repayment period				10 years
PGCB loan repayment expense		156,000	155,000	$ 469,000	468,000
Horsemen's Agreement
Commitments and Contingencies [Line Items]
Purses earned by horsemen and other fees outstanding		6,400,000		6,400,000		$ 7,400,000
Priority Distribution Agreement
Commitments and Contingencies [Line Items]
Minimum annual limit of priority distribution payments				40,000,000
Priority distribution payments		$ 10,000,000	$ 10,000,000	$ 30,000,000	$ 21,500,000