Capitalization (Narrative) (Details) $ in Millions		3 Months Ended	6 Months Ended
	Feb. 28, 2022 USD ($) bank	Mar. 31, 2024 USD ($) shares	Mar. 31, 2024 USD ($) shares	Feb. 26, 2027 USD ($)	Apr. 10, 2024 USD ($)	Mar. 08, 2024 USD ($)	Feb. 14, 2024 USD ($) lender	Sep. 30, 2023 USD ($)
Debt Instrument [Line Items]
Stock repurchase program, authorized amount						$ 200.0
Current Portion of Long-Term Debt		$ 0.0	$ 0.0					$ 0.0
Stock and Benefit Plans
Debt Instrument [Line Items]
Share Repurchases (in shares) | shares			77,426
Share Repurchase Plan
Debt Instrument [Line Items]
Share Repurchases (in shares) | shares		96,133
Share Repurchases		$ 5.0
364-Day Credit Agreement
Debt Instrument [Line Items]
Term	364 days
Term Loan Agreement
Debt Instrument [Line Items]
Maximum borrowing capacity							$ 300.0
Number of lenders | lender							6
Term Loan Agreement | Subsequent Event
Debt Instrument [Line Items]
Long-term debt, face amount					$ 300.0
Credit Agreement
Debt Instrument [Line Items]
Number of banks In syndicate | bank	12
Maximum borrowing capacity	$ 1,000.0
Credit Agreement | Forecast
Debt Instrument [Line Items]
Maximum borrowing capacity				$ 940.0
Restricted Stock Units
Debt Instrument [Line Items]
Common stock issued (in shares) | shares			112,632
Performance Shares
Debt Instrument [Line Items]
Common stock issued (in shares) | shares			251,255
Board Of Directors
Debt Instrument [Line Items]
Common stock issued (in shares) | shares			18,432
Officer DCP Plan
Debt Instrument [Line Items]
Common stock issued (in shares) | shares			3,559