Shareholders' Equity - Schedule of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021
Accumulated Other Comprehensive Income (Loss), Net Of Tax [Roll Forward]
Beginning balance	$ 638	$ 565	$ 615	$ 495
Other comprehensive income (loss) before reclassification	16	(22)	2	35
Amounts reclassified from accumulated other comprehensive loss	0	2	2	4
Net current-period other comprehensive income (loss)	16	(20)	4	39
Ending Balance	720	613	720	613
Foreign Currency Translation
Accumulated Other Comprehensive Income (Loss), Net Of Tax [Roll Forward]
Beginning balance	(119)	(74)	(105)	(129)
Other comprehensive income (loss) before reclassification	15	(22)	1	33
Amounts reclassified from accumulated other comprehensive loss	0	0	0	0
Net current-period other comprehensive income (loss)	15	(22)	1	33
Ending Balance	(104)	(96)	(104)	(96)
Employee Benefit Related Adjustments
Accumulated Other Comprehensive Income (Loss), Net Of Tax [Roll Forward]
Beginning balance	(525)	(480)	(526)	(483)
Other comprehensive income (loss) before reclassification	2	0	1	1
Amounts reclassified from accumulated other comprehensive loss	0	2	2	4
Net current-period other comprehensive income (loss)	2	2	3	5
Ending Balance	(523)	(478)	(523)	(478)
Unrealized Income (Loss) on cash flow hedges
Accumulated Other Comprehensive Income (Loss), Net Of Tax [Roll Forward]
Beginning balance	0	(1)	(1)	(2)
Other comprehensive income (loss) before reclassification	(1)	0	0	1
Amounts reclassified from accumulated other comprehensive loss	0	0	0	0
Net current-period other comprehensive income (loss)	(1)	0	0	1
Ending Balance	(1)	(1)	(1)	(1)
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss), Net Of Tax [Roll Forward]
Beginning balance	(644)	(555)	(632)	(614)
Ending Balance	$ (628)	$ (575)	$ (628)	$ (575)