Shareholders' Equity - Schedule of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Shareholders' equity, beginning balance	$ 9,419,091	$ 7,906,889	$ 6,791,203
Other comprehensive income (loss) before reclassifications	151,536	296,333
Amounts reclassified from accumulated other comprehensive income	(2,120)	2,976
Net current-period other comprehensive income (loss)	149,416	299,309	127,392
Shareholders' equity, ending balance	10,870,064	9,419,091	7,906,889
Available- for-Sale Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Shareholders' equity, beginning balance	(495)	47
Other comprehensive income (loss) before reclassifications	126	(542)
Amounts reclassified from accumulated other comprehensive income	0	0
Net current-period other comprehensive income (loss)	126	(542)
Shareholders' equity, ending balance	(369)	(495)	47
Interest Rate Agreement Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Shareholders' equity, beginning balance	369,607	69,756
Other comprehensive income (loss) before reclassifications	151,410	296,875
Amounts reclassified from accumulated other comprehensive income	(2,120)	2,976
Net current-period other comprehensive income (loss)	149,290	299,851
Shareholders' equity, ending balance	518,897	369,607	69,756
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Shareholders' equity, beginning balance	369,112	69,803	(57,589)
Net current-period other comprehensive income (loss)	149,416	299,309	127,392
Shareholders' equity, ending balance	$ 518,528	$ 369,112	$ 69,803