Stock Incentive Plans - Components of Pre-Tax Stock-Based Compensation Expense Included in Continuing Operations (Parenthetical) (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Mar. 31, 2022		Mar. 31, 2021		Mar. 31, 2022		Mar. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 5	[1]	$ 5	[2]	$ 11	[1]	$ 10	[2]
Cash-settled Nonvested Restricted Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 0		$ 1		$ 2		$ 2

[1] Included zero and $2 million of expense related to cash-settled nonvested restricted stock awards during the three and six months ended March 31, 2022.

[2] Included $1 million and $2 million of expense related to cash-settled nonvested restricted stock awards during the three and six months ended March 31, 2021.