Derivative Instruments and Hedging Activities - Narrative (Details) - USD ($) |
1 Months Ended | 3 Months Ended | 6 Months Ended | |||
|---|---|---|---|---|---|---|
Mar. 31, 2023 |
Mar. 31, 2025 |
Mar. 31, 2024 |
Mar. 31, 2025 |
Mar. 31, 2024 |
Sep. 30, 2024 |
|
| Derivative [Line Items] | ||||||
| Net gains (losses) on derivative instruments | $ (4,000,000) | $ 12,000,000 | $ 11,000,000 | $ (3,000,000) | ||
| Pre-tax gains (losses) associated with net investment hedges | (33,000,000) | 17,000,000 | 22,000,000 | (15,000,000) | ||
| Maximum amount of loss | 256,000,000 | 256,000,000 | ||||
| Cash collateral received | 45,000,000 | 6,000,000 | 45,000,000 | 6,000,000 | $ 14,000,000 | |
| Revolver | Credit Agreement | ||||||
| Derivative [Line Items] | ||||||
| Net gains (losses) on derivative instruments | $ 32,000,000 | |||||
| IRPAs | ||||||
| Derivative [Line Items] | ||||||
| Notional amount | 0 | $ 0 | 0 | $ 0 | $ 0 | |
| Pre-tax net gains associated with interest rate hedges | $ 8,000,000 | $ 8,000,000 | ||||
| Forward foreign currency exchange contracts | ||||||
| Derivative [Line Items] | ||||||
| Derivative notional amount percent of required need coverage | 90.00% | 90.00% | ||||