Shareholders' Equity - Schedule of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Shareholders' equity, beginning balance	$ 12,157,669	$ 10,870,064	$ 9,419,091
Other comprehensive income (loss) before reclassifications	24,204	(42,848)
Amounts reclassified from accumulated other comprehensive income	(14,904)	(9,965)
Total other comprehensive income (loss)	9,300	(52,813)	149,416
Shareholders' equity, ending balance	13,558,890	12,157,669	10,870,064
Available- for-Sale Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Shareholders' equity, beginning balance	213	(369)
Other comprehensive income (loss) before reclassifications	(4)	582
Amounts reclassified from accumulated other comprehensive income	0	0
Total other comprehensive income (loss)	(4)	582
Shareholders' equity, ending balance	209	213	(369)
Interest Rate Agreement Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Shareholders' equity, beginning balance	465,502	518,897
Other comprehensive income (loss) before reclassifications	24,208	(43,430)
Amounts reclassified from accumulated other comprehensive income	(14,904)	(9,965)
Total other comprehensive income (loss)	9,304	(53,395)
Shareholders' equity, ending balance	474,806	465,502	518,897
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Shareholders' equity, beginning balance	465,715	518,528	369,112
Total other comprehensive income (loss)	9,300	(52,813)	149,416
Shareholders' equity, ending balance	$ 475,015	$ 465,715	$ 518,528