SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, RISKS AND UNCERTAINTIES - Recent Accounting Pronouncements and Analysis of the Effects on the Financial Statements (Details) - USD ($)		3 Months Ended	12 Months Ended
	Oct. 01, 2018	Jun. 30, 2019	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash provided by operating activities			$ 855,751,000	$ 557,852,000	$ 371,199,000
Net cash used in financing activities			$ (376,329,000)	(319,814,000)	(300,829,000)
ASU 2016-18 | Adjustments
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash provided by operating activities				2,696,000	9,568,000
Net cash used in financing activities				0
ASU 2016-15 | Adjustments
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash provided by operating activities				10,625,000	0
Net cash used in financing activities				$ (10,625,000)	$ 0
ASU 2016-01 | Adjustments
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification of cumulative gains, before tax	$ 44,000,000
Reclassification of cumulative gains, after tax	$ 29,100,000
ASU 2018-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification of stranded tax effect		$ 4,200,000