Debt - Senior Notes (Details) - Senior Notes - USD ($) $ in Thousands	Sep. 30, 2025	Sep. 30, 2024
Debt Instrument [Line Items]
Face Value	$ 2,800,000	$ 1,300,000
Fair Value	2,793,500	1,263,500
The 2018 Senior Notes
Debt Instrument [Line Items]
Face Value	400,000	400,000
Fair Value	399,500	399,500
The 2019 Senior Notes and the 2021 Senior Notes
Debt Instrument [Line Items]
Face Value	900,000	900,000
Fair Value	875,250	864,000
The 2025 Senior Notes
Debt Instrument [Line Items]
Face Value	1,500,000	0
Fair Value	$ 1,518,750	$ 0