Senior Notes (Details) - USD ($)	Dec. 17, 2021	Dec. 06, 2019	May 08, 2018	Sep. 30, 2024	Sep. 30, 2023
Debt Instrument [Line Items]
Total Senior Notes				$ 1,300,000,000	$ 1,300,000,000
The 2018 Senior Notes
Debt Instrument [Line Items]
Total Senior Notes				400,000,000	400,000,000
Fair value				399,500,000	386,000,000
The 2019 and 2021 Senior Notes
Debt Instrument [Line Items]
Total Senior Notes				900,000,000	900,000,000
Fair value				864,000,000	803,250,000
Senior Notes
Debt Instrument [Line Items]
2026				400,000,000
2027				0
2028				900,000,000
Fair value				$ 1,263,500,000	$ 1,189,250,000
Senior Notes | The 2018 Senior Notes
Debt Instrument [Line Items]
Debt Instrument, Face Amount			$ 400,000,000
Interest rate			5.25%
Maturity date			May 15, 2026
Senior Notes | May 2018 Senior Notes
Debt Instrument [Line Items]
Debt Instrument, Face Amount			$ 350,000,000
Interest rate			4.00%
Maturity date		Jun. 15, 2028
Senior Notes | Senior Notes December 2021
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 550,000,000
Interest rate	4.00%
Maturity date	Jun. 15, 2028