v3.26.1
Segment Information - Schedule of Information about Segment Revenue, Segment Expenses, and Net Income (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Mar. 31, 2026
Mar. 31, 2025
Segment Reporting Information [Line Items]        
Gas utility operating revenues $ 1,020.0 $ 976.4 $ 1,718.7 $ 1,594.4
Depreciation and amortization expense 84.5 72.4 162.2 143.3
Interest expense 62.6 45.3 120.6 91.5
Income Tax Expense 52.7 46.3 74.1 63.5
Net Income From Discontinued Operations, net of tax 64.6 20.0 71.8 29.2
Net Income 282.2 209.3 377.2 290.6
Operating Segments [Member] | Gas Utility [Member]        
Segment Reporting Information [Line Items]        
Gas utility operating revenues 1,014.9 970.2 1,708.2 1,583.7
Cost of gas sold, incl. gross receipts taxes 460.2 485.9 773.3 767.2
Operation and maintenance expense 122.0 122.8 241.7 237.8
Depreciation and amortization expense 81.6 69.5 156.4 137.6
Interest expense 35.3 33.8 72.1 68.9
Income Tax Expense 56.4 45.2 80.5 61.3
Other segment items [1] 32.7 24.0 59.0 48.6
Other net loss [2] (14.2) (5.9) (30.3) (11.6)
Net Income From Discontinued Operations, net of tax 64.6 20.0 71.8 29.2
Net Income 282.2 209.3 377.2 290.6
Capital expenditures 187.9 177.3 384.6 395.1
Intersegment Eliminations [Member]        
Segment Reporting Information [Line Items]        
Gas utility operating revenues [3] $ 5.1 $ 6.2 $ 10.5 $ 10.7
[1] Other segment items include taxes other than income excluding gross receipt tax, and miscellaneous income and deductions.
[2] Other net loss of the Company's consolidated information include Spire's subsidiaries include subsidiaries engaged in the transportation of natural gas, risk management, among other activities, and unallocated corporate items, including transition and transaction cost associated with the Tennessee acquisition and financing costs.
[3] Includes other operating revenues net of elimination of Spire subsidiaries noted in (b) above.