Capitalization and Short-Term Borrowings - Schedule of Long-Term Debt (Details) - USD ($) $ in Thousands		12 Months Ended
		Sep. 30, 2023	Sep. 30, 2022	May 18, 2023	Mar. 31, 2023	Nov. 25, 2022	Feb. 24, 2021
Debt Instrument [Line Items]
Total Long-Term Debt		$ 2,400,000	$ 2,649,000
Less Unamortized Discount and Debt Issuance Costs		15,515	16,591
Less Current Portion	[1]	0	549,000
Long-Term Debt, Net of Current Portion and Unamortized Discount and Debt Issuance Costs		2,384,485	2,083,409
7.4% due June 2025
Debt Instrument [Line Items]
Medium-Term Notes	[2]	$ 50,000	$ 99,000
Long-term debt, interest rate		7.40%	7.40%
2.95% to 5.50% due July 2025 to March 2031
Debt Instrument [Line Items]
Notes	[2],[3],[4]	$ 2,350,000	$ 2,550,000
Percentage of principal amount		101.00%	101.00%
4.75% Notes Due September 1, 2028
Debt Instrument [Line Items]
Long-term debt, interest rate		4.75%
Long-term debt, face value		$ 300,000
Maximum interest rate adjustment		2.00%
3.95% Notes Due September 15, 2027
Debt Instrument [Line Items]
Long-term debt, interest rate		3.95%
Long-term debt, face value		$ 300,000
Maximum interest rate adjustment		2.00%
2.95% Notes Due March 1, 2031
Debt Instrument [Line Items]
Long-term debt, interest rate		2.95%					2.95%
Long-term debt, face value		$ 500,000					$ 500,000
Maximum interest rate adjustment		2.00%
5.50% Notes Due January 15, 2026
Debt Instrument [Line Items]
Long-term debt, interest rate		5.50%
Long-term debt, face value		$ 500,000
Maximum interest rate adjustment		2.00%
5.50% Notes Due October 1, 2026
Debt Instrument [Line Items]
Long-term debt, interest rate		5.50%		5.50%
Long-term debt, face value		$ 300,000		$ 300,000
3.75% Notes Due March 2023
Debt Instrument [Line Items]
Less Current Portion			$ 500,000
Long-term debt, interest rate			3.75%		3.75%	3.75%
Debt instrument redeemed					$ 350,000	$ 150,000
7.395% Notes Due March 2023
Debt Instrument [Line Items]
Less Current Portion			$ 49,000
Long-term debt, interest rate			7.395%		7.395%
Debt instrument redeemed					$ 49,000
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] None of the Company's long-term debt as of September 30, 2023 had a maturity date within the following twelve-month period. Current Portion of Long-Term Debt at September 30, 2022 consisted of $500.0 million of 3.75% notes and $49.0 million of 7.395% notes. The Company redeemed $150.0 million of the 3.75% notes on November 25, 2022 using a portion of the proceeds from short-term borrowings, as discussed below. In March 2023, the Company redeemed the remaining $350.0 million of the 3.75% notes as well as the $49.0 million of 7.395% notes

[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.