SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - RECENTLY ADOPTED ACCOUNTING STANDARDS (Details) - USD ($) $ in Thousands		12 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Accounting Policies [Abstract]
Reclassifications of certain income tax effects to retained earnings	[1]	$ 3,300
Equity reclass		1,418,978	$ 1,236,643	$ 1,166,591	$ 1,106,956
Deferred gain, unamortized balance		$ (6,800)

[1] Due to the adoption of ASU No. 2018-02, an amendment to ASC 740, Income Taxes. See Note 2. Summary of Significant Accounting Policies - Recently Adopted Updates to the Accounting Standards Codification section for more details.