NEW ACCOUNTING STANDARDS - Income Statement Impacts (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenues:
Gross revenues	$ 347,607	$ 369,552	$ 974,804	$ 1,080,884
Less-Promotional allowances	0	(24,649)	0	(72,480)
Net revenues	347,607	344,903	974,804	1,008,404
Operating costs and expenses:
Advertising, general and administrative	53,534	49,093	149,664	149,065
Corporate	13,839	13,008	38,728	39,251
Depreciation and amortization	22,810	20,664	92,682	60,699
Other, net	2,910	4,099	6,357	8,935
Total operating costs and expenses	292,397	280,999	853,998	833,428
Income from operations	55,210	63,904	120,806	174,976
Gaming
Revenues:
Gross revenues	235,418	295,417	669,172	871,158
Operating costs and expenses:
Cost of goods sold	135,238	164,108	389,872	490,224
Food and beverage
Revenues:
Gross revenues	37,171	22,386	105,485	65,376
Operating costs and expenses:
Cost of goods sold	29,080	10,552	81,611	30,921
Hotel
Revenues:
Gross revenues	23,794	15,711	68,776	45,575
Operating costs and expenses:
Cost of goods sold	12,052	6,945	31,881	20,597
Retail, entertainment and other
Revenues:
Gross revenues	51,224	36,038	131,371	98,775
Operating costs and expenses:
Cost of goods sold	22,934	$ 12,530	63,203	$ 33,736
Balance without Adoption of ASC 606
Revenues:
Gross revenues	378,000		1,057,968
Less-Promotional allowances	(27,709)		(73,793)
Net revenues	350,291		984,175
Operating costs and expenses:
Advertising, general and administrative	53,425		149,305
Corporate	13,839		38,728
Depreciation and amortization	22,810		92,682
Other, net	2,910		6,357
Total operating costs and expenses	295,474		865,888
Income from operations	54,817		118,287
Balance without Adoption of ASC 606 | Gaming
Revenues:
Gross revenues	286,739		814,922
Operating costs and expenses:
Cost of goods sold	174,279		481,906
Balance without Adoption of ASC 606 | Food and beverage
Revenues:
Gross revenues	25,924		71,266
Operating costs and expenses:
Cost of goods sold	4,815		34,649
Balance without Adoption of ASC 606 | Hotel
Revenues:
Gross revenues	17,488		50,064
Operating costs and expenses:
Cost of goods sold	8,980		23,495
Balance without Adoption of ASC 606 | Retail, entertainment and other
Revenues:
Gross revenues	47,849		121,716
Operating costs and expenses:
Cost of goods sold	14,416		38,766
Effect of Change Higher/(Lower) | Accounting Standards Update 2014-09
Revenues:
Gross revenues	(30,393)		(83,164)
Less-Promotional allowances	27,709		73,793
Net revenues	(2,684)		(9,371)
Operating costs and expenses:
Advertising, general and administrative	109		359
Corporate	0		0
Depreciation and amortization	0		0
Other, net	0		0
Total operating costs and expenses	(3,077)		(11,890)
Income from operations	393		2,519
Effect of Change Higher/(Lower) | Accounting Standards Update 2014-09 | Gaming
Revenues:
Gross revenues	(51,321)		(145,750)
Operating costs and expenses:
Cost of goods sold	(39,041)		(92,034)
Effect of Change Higher/(Lower) | Accounting Standards Update 2014-09 | Food and beverage
Revenues:
Gross revenues	11,247		34,219
Operating costs and expenses:
Cost of goods sold	24,265		46,962
Effect of Change Higher/(Lower) | Accounting Standards Update 2014-09 | Hotel
Revenues:
Gross revenues	6,306		18,712
Operating costs and expenses:
Cost of goods sold	3,072		8,386
Effect of Change Higher/(Lower) | Accounting Standards Update 2014-09 | Retail, entertainment and other
Revenues:
Gross revenues	3,375		9,655
Operating costs and expenses:
Cost of goods sold	8,518		24,437
Effect of Change Higher/(Lower) | Accounting Standards Update 2014-09 | Loyalty Points
Revenues:
Gross revenues	599		2,114
Less-Promotional allowances	0		0
Net revenues	599		2,114
Operating costs and expenses:
Advertising, general and administrative	0		0
Corporate	0		0
Depreciation and amortization	0		0
Other, net	0		0
Total operating costs and expenses	206		(405)
Income from operations	393		2,519
Effect of Change Higher/(Lower) | Accounting Standards Update 2014-09 | Loyalty Points | Gaming
Revenues:
Gross revenues	599		2,114
Operating costs and expenses:
Cost of goods sold	206		(405)
Effect of Change Higher/(Lower) | Accounting Standards Update 2014-09 | Loyalty Points | Food and beverage
Revenues:
Gross revenues	0		0
Operating costs and expenses:
Cost of goods sold	0		0
Effect of Change Higher/(Lower) | Accounting Standards Update 2014-09 | Loyalty Points | Hotel
Revenues:
Gross revenues	0		0
Operating costs and expenses:
Cost of goods sold	0		0
Effect of Change Higher/(Lower) | Accounting Standards Update 2014-09 | Loyalty Points | Retail, entertainment and other
Revenues:
Gross revenues	0		0
Operating costs and expenses:
Cost of goods sold	0		0
Effect of Change Higher/(Lower) | Accounting Standards Update 2014-09 | Promotional Allowances (Discretionary Complementaries)
Revenues:
Gross revenues	(20,249)		(49,883)
Less-Promotional allowances	21,438		53,445
Net revenues	1,189		3,562
Operating costs and expenses:
Advertising, general and administrative	0		0
Corporate	0		0
Depreciation and amortization	0		0
Other, net	0		0
Total operating costs and expenses	1,189		3,562
Income from operations	0		0
Effect of Change Higher/(Lower) | Accounting Standards Update 2014-09 | Promotional Allowances (Discretionary Complementaries) | Gaming
Revenues:
Gross revenues	(41,089)		(110,772)
Operating costs and expenses:
Cost of goods sold	(12,755)		(16,186)
Effect of Change Higher/(Lower) | Accounting Standards Update 2014-09 | Promotional Allowances (Discretionary Complementaries) | Food and beverage
Revenues:
Gross revenues	10,266		31,264
Operating costs and expenses:
Cost of goods sold	13,944		19,748
Effect of Change Higher/(Lower) | Accounting Standards Update 2014-09 | Promotional Allowances (Discretionary Complementaries) | Hotel
Revenues:
Gross revenues	6,130		18,204
Operating costs and expenses:
Cost of goods sold	0		0
Effect of Change Higher/(Lower) | Accounting Standards Update 2014-09 | Promotional Allowances (Discretionary Complementaries) | Retail, entertainment and other
Revenues:
Gross revenues	4,444		11,421
Operating costs and expenses:
Cost of goods sold	0		0
Effect of Change Higher/(Lower) | Accounting Standards Update 2014-09 | Promotional Allowances (Non-Discretionary Complementaries)
Revenues:
Gross revenues	(13,449)		(43,737)
Less-Promotional allowances	5,486		18,046
Net revenues	(7,963)		(25,691)
Operating costs and expenses:
Advertising, general and administrative	0		0
Corporate	0		0
Depreciation and amortization	0		0
Other, net	0		0
Total operating costs and expenses	(7,963)		(25,691)
Income from operations	0		0
Effect of Change Higher/(Lower) | Accounting Standards Update 2014-09 | Promotional Allowances (Non-Discretionary Complementaries) | Gaming
Revenues:
Gross revenues	(14,690)		(47,867)
Operating costs and expenses:
Cost of goods sold	(30,644)		(86,925)
Effect of Change Higher/(Lower) | Accounting Standards Update 2014-09 | Promotional Allowances (Non-Discretionary Complementaries) | Food and beverage
Revenues:
Gross revenues	0		0
Operating costs and expenses:
Cost of goods sold	9,340		24,259
Effect of Change Higher/(Lower) | Accounting Standards Update 2014-09 | Promotional Allowances (Non-Discretionary Complementaries) | Hotel
Revenues:
Gross revenues	0		0
Operating costs and expenses:
Cost of goods sold	2,896		7,878
Effect of Change Higher/(Lower) | Accounting Standards Update 2014-09 | Promotional Allowances (Non-Discretionary Complementaries) | Retail, entertainment and other
Revenues:
Gross revenues	1,241		4,130
Operating costs and expenses:
Cost of goods sold	10,445		29,097
Effect of Change Higher/(Lower) | Accounting Standards Update 2014-09 | Cash Promotions
Revenues:
Gross revenues	(1,568)		(5,827)
Less-Promotional allowances	0		0
Net revenues	(1,568)		(5,827)
Operating costs and expenses:
Advertising, general and administrative	0		0
Corporate	0		0
Depreciation and amortization	0		0
Other, net	0		0
Total operating costs and expenses	(1,568)		(5,827)
Income from operations	0		0
Effect of Change Higher/(Lower) | Accounting Standards Update 2014-09 | Cash Promotions | Gaming
Revenues:
Gross revenues	(1,568)		(5,827)
Operating costs and expenses:
Cost of goods sold	(1,568)		(5,827)
Effect of Change Higher/(Lower) | Accounting Standards Update 2014-09 | Cash Promotions | Food and beverage
Revenues:
Gross revenues	0		0
Operating costs and expenses:
Cost of goods sold	0		0
Effect of Change Higher/(Lower) | Accounting Standards Update 2014-09 | Cash Promotions | Hotel
Revenues:
Gross revenues	0		0
Operating costs and expenses:
Cost of goods sold	0		0
Effect of Change Higher/(Lower) | Accounting Standards Update 2014-09 | Cash Promotions | Retail, entertainment and other
Revenues:
Gross revenues	0		0
Operating costs and expenses:
Cost of goods sold	0		0
Effect of Change Higher/(Lower) | Accounting Standards Update 2014-09 | Gross vs. Net Presentation and Other
Revenues:
Gross revenues	4,274		14,169
Less-Promotional allowances	785		2,302
Net revenues	5,059		16,471
Operating costs and expenses:
Advertising, general and administrative	109		359
Corporate	0		0
Depreciation and amortization	0		0
Other, net	0		0
Total operating costs and expenses	5,059		16,471
Income from operations	0		0
Effect of Change Higher/(Lower) | Accounting Standards Update 2014-09 | Gross vs. Net Presentation and Other | Gaming
Revenues:
Gross revenues	5,427		16,602
Operating costs and expenses:
Cost of goods sold	5,720		17,309
Effect of Change Higher/(Lower) | Accounting Standards Update 2014-09 | Gross vs. Net Presentation and Other | Food and beverage
Revenues:
Gross revenues	981		2,955
Operating costs and expenses:
Cost of goods sold	981		2,955
Effect of Change Higher/(Lower) | Accounting Standards Update 2014-09 | Gross vs. Net Presentation and Other | Hotel
Revenues:
Gross revenues	176		508
Operating costs and expenses:
Cost of goods sold	176		508
Effect of Change Higher/(Lower) | Accounting Standards Update 2014-09 | Gross vs. Net Presentation and Other | Retail, entertainment and other
Revenues:
Gross revenues	(2,310)		(5,896)
Operating costs and expenses:
Cost of goods sold	$ (1,927)		$ (4,660)