Segment Reporting (Details) $ in Thousands	3 Months Ended
	Dec. 31, 2021 USD ($) segment	Dec. 31, 2020 USD ($)	Sep. 30, 2021 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment	4
Net Revenues
Net revenues	$ 401,963	$ 230,781
Income (Loss) from Operations
Income (loss) from operations	35,195	10,610
Capital Expenditures Incurred
Capital expenditures incurred	95,111	15,878
Total Assets
Total assets	3,030,554		$ 2,729,877
Operating segments | Mohegan Sun
Net Revenues
Net revenues	251,572	165,891
Income (Loss) from Operations
Income (loss) from operations	61,694	27,247
Capital Expenditures Incurred
Capital expenditures incurred	7,808	2,657
Total Assets
Total assets	1,268,321		1,267,538
Operating segments | Mohegan Sun Pocono
Net Revenues
Net revenues	64,215	38,085
Income (Loss) from Operations
Income (loss) from operations	11,489	1,356
Capital Expenditures Incurred
Capital expenditures incurred	791	1,057
Total Assets
Total assets	404,499		408,187
Operating segments | MGE Niagara Resorts
Net Revenues
Net revenues	62,832	12,997
Income (Loss) from Operations
Income (loss) from operations	6,869	(12,521)
Capital Expenditures Incurred
Capital expenditures incurred	2,719	2,560
Total Assets
Total assets	549,255		561,812
Operating segments | Management, development and other
Net Revenues
Net revenues	13,890	13,315
Income (Loss) from Operations
Income (loss) from operations	(33,971)	2,073
Capital Expenditures Incurred
Capital expenditures incurred	83,773	9,306
Total Assets
Total assets	724,955		407,831
Operating segments | All other
Net Revenues
Net revenues	10,165	0
Income (Loss) from Operations
Income (loss) from operations	(393)	0
Capital Expenditures Incurred
Capital expenditures incurred	13	0
Total Assets
Total assets	102,233		98,945
Corporate
Net Revenues
Net revenues	145	230
Income (Loss) from Operations
Income (loss) from operations	(10,502)	(7,538)
Capital Expenditures Incurred
Capital expenditures incurred	7	298
Total Assets
Total assets	1,011,211		996,040
Inter-segment
Net Revenues
Net revenues	(856)	263
Income (Loss) from Operations
Income (loss) from operations	9	$ (7)
Total Assets
Total assets	$ (1,029,920)		$ (1,010,476)