Consolidated Statements of Comprehensive Income (Loss) (Unaudited) (Parenthetical) - USD ($) $ in Millions	6 Months Ended
Mar. 31, 2022	Mar. 31, 2021
Statement Of Income And Comprehensive Income [Abstract]
Net of tax	$ (1)	$ (3)

Amount of tax expense (benefit) allocated to other comprehensive income (loss).

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+ Details