SEGMENT REPORTING (Details) $ in Thousands	3 Months Ended
	Dec. 31, 2019 USD ($) segment	Dec. 31, 2018 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment	3
Segment data [Abstract]
Net interest income	$ 64,651	$ 60,272
Provision for loan and lease losses	3,407	9,099
Noninterest income	37,483	37,751
Noninterest expense	75,798	74,295
Income (loss) before income tax expense (benefit)	22,929	14,629
Total assets	6,180,926	6,182,765	$ 6,182,890
Goodwill	309,505	303,270	309,505	$ 303,270
Total deposits	4,806,580	4,936,447
Consumer
Segment data [Abstract]
Net interest income	20,012	13,674
Provision for loan and lease losses	980	1,973
Noninterest income	24,764	22,891
Noninterest expense	16,783	18,129
Income (loss) before income tax expense (benefit)	27,013	16,463
Total assets	720,873	612,999
Goodwill	87,145	87,145	87,145	87,145
Total deposits	2,999,184	2,763,948
Commercial
Segment data [Abstract]
Net interest income	39,736	35,951
Provision for loan and lease losses	3,701	3,854
Noninterest income	14,980	13,932
Noninterest expense	26,726	29,552
Income (loss) before income tax expense (benefit)	24,289	16,477
Total assets	2,494,253	2,074,250
Goodwill	222,360	216,125	222,360	216,125
Total deposits	13,855	7,177
Corporate Services/Other
Segment data [Abstract]
Net interest income	4,903	10,647
Provision for loan and lease losses	(1,274)	3,272
Noninterest income	(2,261)	928
Noninterest expense	32,289	26,614
Income (loss) before income tax expense (benefit)	(28,373)	(18,311)
Total assets	2,965,800	3,495,516
Goodwill	0	0	$ 0	$ 0
Total deposits	$ 1,793,541	$ 2,165,322