CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) Statement - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 1,360	$ 1,135	$ 500
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, after Tax	1	25	99
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, after Tax	(3)	(48)	(42)
Total other comprehensive income (loss)	(2)	(23)	57
Total comprehensive income (loss)	$ 1,358	$ 1,112	$ 557