REPORTING SEGMENT AND OTHER OPERATIONS DATA - RECONCILIATION OF SEGMENT INCOME TO CONSOLIDATED (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Utility	$ 357,409	$ 274,435
Nonutility	366,158	401,407
Operating revenues	723,567	675,842
Depreciation and amortization	36,683	30,393
Interest income	1,959	501
Interest expense, net of capitalized interest	29,491	19,477
Income tax provision (benefit)	32,978	30,807
Equity in earnings of affiliates	946	575
Net financial earnings (loss)	110,284	65,770
Capital expenditures	145,923	164,298
Energy Services
Segment Reporting Information [Line Items]
Operating revenues	20,000	22,100
Operating Segments
Segment Reporting Information [Line Items]
Operating revenues	719,158	666,342
Depreciation and amortization	36,465	30,287
Interest income	2,083	570
Interest expense, net of capitalized interest	29,369	19,233
Income tax provision (benefit)	34,553	32,006
Net financial earnings (loss)	109,858	64,788
Capital expenditures	145,783	164,219
Operating Segments | Natural Gas Distribution, External Customers
Segment Reporting Information [Line Items]
Utility	357,409	274,435
Operating Segments | Clean Energy Ventures, External Customers
Segment Reporting Information [Line Items]
Nonutility	12,792	10,183
Operating Segments | Energy Services
Segment Reporting Information [Line Items]
Nonutility	313,399	365,788
Operating revenues	313,399	365,788
Depreciation and amortization	57	28
Interest income	269	0
Interest expense, net of capitalized interest	3,058	675
Income tax provision (benefit)	20,064	20,505
Net financial earnings (loss)	52,533	17,567
Operating Segments | Storage and Transportation
Segment Reporting Information [Line Items]
Nonutility	25,714	11,584
Operating revenues	25,714	11,584
Depreciation and amortization	5,942	2,133
Interest income	1,401	377
Interest expense, net of capitalized interest	6,707	2,136
Income tax provision (benefit)	1,943	343
Equity in earnings of affiliates	909	1,056
Net financial earnings (loss)	6,243	2,962
Capital expenditures	19,719	65,375
Operating Segments | Natural Gas Distribution
Segment Reporting Information [Line Items]
Operating revenues	357,409	274,435
Depreciation and amortization	24,890	22,893
Interest income	413	193
Interest expense, net of capitalized interest	13,709	10,995
Income tax provision (benefit)	14,383	13,204
Net financial earnings (loss)	54,664	51,080
Capital expenditures	82,071	73,464
Operating Segments | Clean Energy Ventures
Segment Reporting Information [Line Items]
Operating revenues	12,792	10,183
Depreciation and amortization	5,576	5,233
Interest expense, net of capitalized interest	5,895	5,427
Income tax provision (benefit)	(1,837)	(2,046)
Net financial earnings (loss)	(3,582)	(6,821)
Capital expenditures	43,993	25,380
Intercompany
Segment Reporting Information [Line Items]
Nonutility	13	99
Intercompany | Natural Gas Distribution, External Customers
Segment Reporting Information [Line Items]
Utility	337	337
Intercompany | Energy Services
Segment Reporting Information [Line Items]
Nonutility	8,383	3,456
Intercompany | Storage and Transportation
Segment Reporting Information [Line Items]
Nonutility	1,124	559
Home Services and Other
Segment Reporting Information [Line Items]
Nonutility	14,253	13,852
Operating revenues	14,253	13,852
Depreciation and amortization	218	204
Interest income	654	155
Interest expense, net of capitalized interest	122	244
Income tax provision (benefit)	217	246
Net financial earnings (loss)	(29)	447
Capital expenditures	140	79
Eliminations
Segment Reporting Information [Line Items]
Nonutility	(9,857)	(4,451)
Depreciation and amortization	0	(98)
Interest income	(778)	(224)
Income tax provision (benefit)	(1,792)	(1,445)
Equity in earnings of affiliates	37	(481)
Net financial earnings (loss)	$ 455	$ 535