SUMMARY OF CASH DISTRIBUTIONS TO COMMON SHAREHOLDERS (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cash distributions paid to common shareholders, Amount	$ 63,742	$ 53,586	$ 46,289
Cash distributions paid to common shareholders, Per Share	$ 0.68	$ 0.68	$ 0.64
December 31 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cash distributions paid to common shareholders, Amount	$ 15,570	$ 13,017	$ 11,184
Cash distributions paid to common shareholders, Per Share	$ 0.17	$ 0.17	$ 0.16
March 31 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cash distributions paid to common shareholders, Amount	$ 15,825	$ 13,303	$ 11,429
Cash distributions paid to common shareholders, Per Share	$ 0.17	$ 0.17	$ 0.16
June 30 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cash distributions paid to common shareholders, Amount	$ 16,064	$ 13,523	$ 11,698
Cash distributions paid to common shareholders, Per Share	$ 0.17	$ 0.17	$ 0.16
September 30 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cash distributions paid to common shareholders, Amount	$ 16,283	$ 13,743	$ 11,978
Cash distributions paid to common shareholders, Per Share	$ 0.17	$ 0.17	$ 0.16