Shareholders' Equity - Schedule of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Shareholders' equity, beginning balance	$ 10,870,064	$ 9,419,091	$ 7,906,889
Other comprehensive income (loss) before reclassifications	(42,848)	151,536
Amounts reclassified from accumulated other comprehensive income	(9,965)	(2,120)
Total other comprehensive income (loss)	(52,813)	149,416	299,309
Shareholders' equity, ending balance	12,157,669	10,870,064	9,419,091
Available- for-Sale Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Shareholders' equity, beginning balance	(369)	(495)
Other comprehensive income (loss) before reclassifications	582	126
Amounts reclassified from accumulated other comprehensive income	0	0
Total other comprehensive income (loss)	582	126
Shareholders' equity, ending balance	213	(369)	(495)
Interest Rate Agreement Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Shareholders' equity, beginning balance	518,897	369,607
Other comprehensive income (loss) before reclassifications	(43,430)	151,410
Amounts reclassified from accumulated other comprehensive income	(9,965)	(2,120)
Total other comprehensive income (loss)	(53,395)	149,290
Shareholders' equity, ending balance	465,502	518,897	369,607
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Shareholders' equity, beginning balance	518,528	369,112	69,803
Total other comprehensive income (loss)	(52,813)	149,416	299,309
Shareholders' equity, ending balance	$ 465,715	$ 518,528	$ 369,112