ORGANIZATION AND BASIS OF PRESENTATION - Revenue Disaggregation (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Disaggregation of Revenue [Line Items]
Net revenues	$ 278,628	$ 314,701	$ 509,409	$ 713,753
Connecticut
Disaggregation of Revenue [Line Items]
Net revenues	189,022	182,286	354,913	425,621
Pennsylvania
Disaggregation of Revenue [Line Items]
Net revenues	52,376	53,102	90,461	115,056
Nevada
Disaggregation of Revenue [Line Items]
Net revenues	1,715	0	1,715	0
Canada
Disaggregation of Revenue [Line Items]
Net revenues	13,816	71,282	26,813	156,256
Other
Disaggregation of Revenue [Line Items]
Net revenues	21,151	8,574	34,696	17,694
Gaming
Disaggregation of Revenue [Line Items]
Net revenues	209,184	215,994	382,385	480,263
Gaming | Connecticut
Disaggregation of Revenue [Line Items]
Net revenues	145,965	124,721	270,990	284,980
Gaming | Pennsylvania
Disaggregation of Revenue [Line Items]
Net revenues	49,019	45,409	84,661	97,387
Gaming | Nevada
Disaggregation of Revenue [Line Items]
Net revenues	1,515	0	1,515	0
Gaming | Canada
Disaggregation of Revenue [Line Items]
Net revenues	12,685	45,864	25,219	97,896
Gaming | Other
Disaggregation of Revenue [Line Items]
Net revenues	0	0	0	0
Food and beverage
Disaggregation of Revenue [Line Items]
Net revenues	13,343	37,557	24,383	88,089
Food and beverage | Connecticut
Disaggregation of Revenue [Line Items]
Net revenues	12,047	21,422	22,252	49,955
Food and beverage | Pennsylvania
Disaggregation of Revenue [Line Items]
Net revenues	1,132	4,586	1,973	10,668
Food and beverage | Nevada
Disaggregation of Revenue [Line Items]
Net revenues	177	0	177	0
Food and beverage | Canada
Disaggregation of Revenue [Line Items]
Net revenues	0	11,591	0	27,544
Food and beverage | Other
Disaggregation of Revenue [Line Items]
Net revenues	(13)	(42)	(19)	(78)
Hotel
Disaggregation of Revenue [Line Items]
Net revenues	17,170	20,115	33,694	47,704
Hotel | Connecticut
Disaggregation of Revenue [Line Items]
Net revenues	16,088	15,875	31,808	37,923
Hotel | Pennsylvania
Disaggregation of Revenue [Line Items]
Net revenues	1,093	1,484	1,897	3,464
Hotel | Nevada
Disaggregation of Revenue [Line Items]
Net revenues	0	0	0	0
Hotel | Canada
Disaggregation of Revenue [Line Items]
Net revenues	0	2,756	0	6,319
Hotel | Other
Disaggregation of Revenue [Line Items]
Net revenues	(11)	0	(11)	(2)
Retail, entertainment and other
Disaggregation of Revenue [Line Items]
Net revenues	38,931	41,035	68,947	97,697
Retail, entertainment and other | Connecticut
Disaggregation of Revenue [Line Items]
Net revenues	14,922	20,268	29,863	52,763
Retail, entertainment and other | Pennsylvania
Disaggregation of Revenue [Line Items]
Net revenues	1,132	1,623	1,930	3,537
Retail, entertainment and other | Nevada
Disaggregation of Revenue [Line Items]
Net revenues	23	0	23	0
Retail, entertainment and other | Canada
Disaggregation of Revenue [Line Items]
Net revenues	1,131	11,071	1,594	24,497
Retail, entertainment and other | Other
Disaggregation of Revenue [Line Items]
Net revenues	2,581	162	2,817	308
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	$ 18,594	$ 8,454	$ 31,909	$ 17,466