Capitalization and Short-Term Borrowings - Schedule of Long-Term Debt (Details) - USD ($) $ in Thousands		12 Months Ended
		Sep. 30, 2024	Sep. 30, 2023	May 18, 2023
Debt Instrument [Line Items]
Total Long-Term Debt		$ 2,700,000	$ 2,400,000
Less Unamortized Discount and Debt Issuance Costs		11,757	15,515
Less Current Portion	[1]	500,000	0
Long-Term Debt, Net of Current Portion and Unamortized Discount and Debt Issuance Costs		2,188,243	2,384,485
7.38% due June 2025
Debt Instrument [Line Items]
Medium-Term Notes	[2]	50,000	$ 50,000
Less Current Portion		$ 50,000
Long-term debt, interest rate		7.38%	7.38%
2.95% to 5.50% due July 2025 to March 2031
Debt Instrument [Line Items]
Notes	[2],[3],[4]	$ 2,350,000	$ 2,350,000
Percentage of principal amount		101.00%	101.00%
Variable Rate due February 2026
Debt Instrument [Line Items]
Long-term debt, face amount	[5]	$ 300,000	$ 0
Long-term debt, weighted average variable interest rate		6.71%
4.62% through December 2024
Debt Instrument [Line Items]
Long-term debt, face amount		$ 200,000
Long-term debt, variable interest rate		4.62%
4.58% until January 2025
Debt Instrument [Line Items]
Long-term debt, face amount		$ 100,000
Long-term debt, variable interest rate		4.58%
4.75% Notes Due September 1, 2028
Debt Instrument [Line Items]
Long-term debt, face amount		$ 300,000
Long-term debt, interest rate		4.75%
Maximum interest rate adjustment		2.00%
3.95% Notes Due September 15, 2027
Debt Instrument [Line Items]
Long-term debt, face amount		$ 300,000
Long-term debt, interest rate		3.95%
Maximum interest rate adjustment		2.00%
2.95% Notes Due March 1, 2031
Debt Instrument [Line Items]
Long-term debt, face amount		$ 500,000
Long-term debt, interest rate		2.95%
Maximum interest rate adjustment		2.00%
5.50% Notes Due January 15, 2026
Debt Instrument [Line Items]
Long-term debt, face amount		$ 500,000
Long-term debt, interest rate		5.50%
Maximum interest rate adjustment		2.00%
5.50% Notes Due October 1, 2026
Debt Instrument [Line Items]
Long-term debt, face amount		$ 300,000		$ 300,000
Long-term debt, interest rate		5.50%		5.50%
Maximum interest rate adjustment		2.00%
5.20% Notes Due July 2025
Debt Instrument [Line Items]
Less Current Portion		$ 450,000
Long-term debt, interest rate		5.20%
Minimum | 2.95% to 5.50% due July 2025 to March 2031
Debt Instrument [Line Items]
Long-term debt, interest rate		2.95%	2.95%
Maximum | 2.95% to 5.50% due July 2025 to March 2031
Debt Instrument [Line Items]
Long-term debt, interest rate		5.50%	5.50%
Maximum | 5.50% Notes Due January 15, 2026
Debt Instrument [Line Items]
Long-term debt, interest rate		7.50%

[1] Current Portion of Long-Term Debt at September 30, 2024 consisted of $50.0 million of 7.38% medium-term notes and $450.0 million of 5.20% notes. None of the Company’s long-term debt as of September 30, 2023 had a maturity date within the following twelve-month period.

[2] The Medium-Term Notes and Notes are unsecured.

[3] The holders of these notes may require the Company to repurchase their notes at a price equal to 101% of the principal amount in the event of both a change in control and a ratings downgrade to a rating below investment grade.

[4] The interest rate payable on $300.0 million of 4.75% notes, $300.0 million of 3.95% notes, $500.0 million of 2.95% notes and $300.0 million of 5.50% notes will be subject to adjustment from time to time, with a maximum of 2.00%, if certain change of control events involving a material subsidiary result in a downgrade of the credit rating assigned to the notes to below investment grade (or if the credit rating assigned to the notes is subsequently upgraded). The interest rate payable on $500.0 million of 5.50% notes will be subject to adjustment from time to time, with a maximum adjustment of 2.00%, such that the coupon will not exceed 7.50%, if there is a downgrade of the credit rating assigned to the notes to a rating below investment grade. A downgrade with a resulting increase to the coupon does not preclude the coupon from returning to its original rate if the Company’s credit rating is subsequently upgraded.

[5] The interest rate on the delayed draw term loan is a weighted average SOFR interest rate of 6.71% that was locked in from April 2024 until the beginning of October 2024. The current locked in interest rate is 4.62% for $200.0 million until December 2024 and 4.58% for the remaining $100.0 million until January 2025.