v3.25.2
Information by Operating Segment - Segment Information by Segment (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Segment Reporting Information [Line Items]        
Revenues from external customers $ 421.9 $ 414.1 $ 2,142.3 $ 2,299.2
Intersegment revenues 0.0 0.0 0.0 0.0
Total Operating Revenues 421.9 414.1 2,142.3 2,299.2
Depreciation and amortization expense 75.7 71.4 221.7 207.3
Interest expense 49.9 48.8 145.3 151.6
Income tax (benefit) expense 3.0 (3.1) 75.8 67.3
Adjusted (loss) earnings 4.1 (4.3) 299.6 275.0
Capital expenditures 220.5 222.2 699.7 631.5
Other Operating Segment [Member]        
Segment Reporting Information [Line Items]        
Revenues from external customers 1.1 0.3 1.9 0.5
Intersegment revenues 4.6 4.5 13.4 12.5
Total Operating Revenues 5.7 4.8 15.3 13.0
Depreciation and amortization expense 0.1 0.2 0.3 0.4
Interest expense 23.5 22.3 72.8 68.6
Income tax (benefit) expense (4.8) (4.7) (6.1) (5.2)
Adjusted (loss) earnings (7.4) (8.2) (29.7) (21.6)
Capital expenditures 0.0 0.0 0.0 0.0
Operating Segments [Member] | Gas Utility [Member]        
Segment Reporting Information [Line Items]        
Revenues from external customers 347.5 371.3 1,931.1 2,158.9
Intersegment revenues 0.0 1.4 0.1 1.7
Total Operating Revenues 347.5 372.7 1,931.2 2,160.6
Depreciation and amortization expense 70.0 66.7 207.6 196.3
Interest expense 33.2 34.9 102.1 112.2
Income tax (benefit) expense (3.0) (0.9) 58.3 56.5
Adjusted (loss) earnings (10.0) (11.0) 263.0 252.8
Capital expenditures 205.9 189.2 601.6 501.4
Operating Segments [Member] | Gas Marketing [Member]        
Segment Reporting Information [Line Items]        
Revenues from external customers 43.1 21.2 129.7 103.5
Intersegment revenues 0.0 0.0 0.0 0.0
Total Operating Revenues 43.1 21.2 129.7 103.5
Depreciation and amortization expense 0.2 0.3 0.9 1.1
Interest expense 0.0 0.0 0.0 0.0
Income tax (benefit) expense 7.3 (1.1) 11.4 10.3
Adjusted (loss) earnings 5.3 1.0 22.3 23.7
Capital expenditures 0.0 0.0 0.1 0.0
Operating Segments [Member] | Midstream [Member]        
Segment Reporting Information [Line Items]        
Revenues from external customers 30.2 21.3 79.6 36.3
Intersegment revenues 12.0 11.2 34.5 32.6
Total Operating Revenues 42.2 32.5 114.1 68.9
Depreciation and amortization expense 5.4 4.2 12.9 9.5
Interest expense 4.1 1.7 6.6 5.5
Income tax (benefit) expense 3.5 3.6 12.2 5.7
Adjusted (loss) earnings 16.2 13.9 44.0 20.1
Capital expenditures 15.3 33.1 99.3 131.1
Consolidation, Eliminations [Member]        
Segment Reporting Information [Line Items]        
Revenues from external customers 0.0 0.0 0.0 0.0
Intersegment revenues (16.6) (17.1) (48.0) (46.8)
Total Operating Revenues (16.6) (17.1) (48.0) (46.8)
Depreciation and amortization expense 0.0 0.0 0.0 0.0
Interest expense (10.9) (10.1) (36.2) (34.7)
Income tax (benefit) expense 0.0 0.0 0.0 0.0
Adjusted (loss) earnings 0.0 0.0 0.0 0.0
Capital expenditures $ (0.7) $ (0.1) $ (1.3) $ (1.0)