ORGANIZATION AND BASIS OF PRESENTATION - Revenue Disaggregation (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disaggregation of Revenue [Line Items]
Net revenues	$ 328,189	$ 107,199	$ 837,598	$ 820,952
Connecticut
Disaggregation of Revenue [Line Items]
Net revenues	220,061	78,239	574,974	503,860
Pennsylvania
Disaggregation of Revenue [Line Items]
Net revenues	62,931	10,512	153,392	125,568
Nevada
Disaggregation of Revenue [Line Items]
Net revenues	8,362	0	10,077	0
Canada
Disaggregation of Revenue [Line Items]
Net revenues	14,380	11,346	41,193	167,602
Other
Disaggregation of Revenue [Line Items]
Net revenues	21,944	6,756	56,640	24,450
Gaming
Disaggregation of Revenue [Line Items]
Net revenues	241,289	89,379	623,674	569,642
Gaming | Connecticut
Disaggregation of Revenue [Line Items]
Net revenues	163,938	67,966	434,928	352,946
Gaming | Pennsylvania
Disaggregation of Revenue [Line Items]
Net revenues	57,134	10,112	141,795	107,499
Gaming | Nevada
Disaggregation of Revenue [Line Items]
Net revenues	6,934	0	8,449	0
Gaming | Canada
Disaggregation of Revenue [Line Items]
Net revenues	13,283	11,301	38,502	109,197
Gaming | Other
Disaggregation of Revenue [Line Items]
Net revenues	0	0	0	0
Food and beverage
Disaggregation of Revenue [Line Items]
Net revenues	20,826	3,009	45,209	91,098
Food and beverage | Connecticut
Disaggregation of Revenue [Line Items]
Net revenues	16,770	2,779	39,022	52,734
Food and beverage | Pennsylvania
Disaggregation of Revenue [Line Items]
Net revenues	2,940	231	4,913	10,899
Food and beverage | Nevada
Disaggregation of Revenue [Line Items]
Net revenues	1,133	0	1,310	0
Food and beverage | Canada
Disaggregation of Revenue [Line Items]
Net revenues	0	0	0	27,544
Food and beverage | Other
Disaggregation of Revenue [Line Items]
Net revenues	(17)	(1)	(36)	(79)
Hotel
Disaggregation of Revenue [Line Items]
Net revenues	22,188	2,589	55,882	50,293
Hotel | Connecticut
Disaggregation of Revenue [Line Items]
Net revenues	20,758	2,568	52,566	40,491
Hotel | Pennsylvania
Disaggregation of Revenue [Line Items]
Net revenues	1,430	21	3,327	3,485
Hotel | Nevada
Disaggregation of Revenue [Line Items]
Net revenues	0	0	0	0
Hotel | Canada
Disaggregation of Revenue [Line Items]
Net revenues	0	0	0	6,319
Hotel | Other
Disaggregation of Revenue [Line Items]
Net revenues	0	0	(11)	(2)
Retail, entertainment and other
Disaggregation of Revenue [Line Items]
Net revenues	43,886	12,222	112,833	109,919
Retail, entertainment and other | Connecticut
Disaggregation of Revenue [Line Items]
Net revenues	18,595	4,926	48,458	57,689
Retail, entertainment and other | Pennsylvania
Disaggregation of Revenue [Line Items]
Net revenues	1,427	148	3,357	3,685
Retail, entertainment and other | Nevada
Disaggregation of Revenue [Line Items]
Net revenues	295	0	318	0
Retail, entertainment and other | Canada
Disaggregation of Revenue [Line Items]
Net revenues	1,097	45	2,691	24,542
Retail, entertainment and other | Other
Disaggregation of Revenue [Line Items]
Net revenues	179	211	2,996	519
Management and development | Connecticut
Disaggregation of Revenue [Line Items]
Net revenues	0	0	0	0
Management and development | Pennsylvania
Disaggregation of Revenue [Line Items]
Net revenues	0	0	0	0
Management and development | Nevada
Disaggregation of Revenue [Line Items]
Net revenues	0	0	0	0
Management and development | Canada
Disaggregation of Revenue [Line Items]
Net revenues	0	0	0	0
Management and development | Other
Disaggregation of Revenue [Line Items]
Net revenues	$ 21,782	$ 6,546	$ 53,691	$ 24,012