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v3.25.1

Fair Value Measurements Fair Value Measurements - Investments (Details) $ in Millions | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Mar. 31, 2025 USD ($) Units | Mar. 31, 2024 USD ($) | Mar. 31, 2025 USD ($) Units | Mar. 31, 2024 USD ($) | Sep. 30, 2024 USD ($)
Investment Gains (Losses) |  |  |  |  |
Financing Receivable, after Allowance for Credit Loss | $ 97 |  | $ 97 |  | $ 99
Period of time where the investor contributes capital to an investment in a private partnership - minimum | Units | 3 |  | 3 |  |
Period of time where the investor contributes capital to an investment in a private partnership - maximum | Units | 4 |  | 4 |  |
Minimum investment period | Units | 10 |  | 10 |  |
Number of readily available quoted exchange prices for the investments | 0 |  | 0 |  |
Investment funds | $ 4,917 |  | $ 4,917 |  | $ 4,968
NDT [Member] |  |  |  |  |
Investment Gains (Losses) |  |  |  |  |
Investment funds | 3,300 |  | 3,300 |  |
ART [Member] |  |  |  |  |
Investment Gains (Losses) |  |  |  |  |
Investment funds | 1,500 |  | 1,500 |  |
LTDCP [Member] |  |  |  |  |
Investment Gains (Losses) |  |  |  |  |
Unrealized gains (losses) on investments | 1 | $ (1) | 2 | $ (2) |
SERP |  |  |  |  |
Investment Gains (Losses) |  |  |  |  |
Unrealized gains (losses) on investments | 0 | (2) | 6 | (9) |
ART [Member] |  |  |  |  |
Investment Gains (Losses) |  |  |  |  |
Unrealized gains (losses) on investments | 8 | (34) | 28 | (123) |
Debt and Equity Securities, Unrealized Gain (Loss) | (6) | 8 | (14) | 24 |
NDT [Member] |  |  |  |  |
Investment Gains (Losses) |  |  |  |  |
Unrealized gains (losses) on investments | (8) | (54) | (67) | (251) |
Debt and Equity Securities, Unrealized Gain (Loss) | (33) | $ 24 | (61) | $ 70 |
Real Estate Funds | NDT [Member] |  |  |  |  |
Investment Gains (Losses) |  |  |  |  |
NDT unfunded commitments related to private equity and real estate | 116 |  | 116 |  |
Real Estate Funds | ART [Member] |  |  |  |  |
Investment Gains (Losses) |  |  |  |  |
NDT unfunded commitments related to private equity and real estate | 63 |  | 63 |  |
Private Equity Funds [Member] | NDT [Member] |  |  |  |  |
Investment Gains (Losses) |  |  |  |  |
NDT unfunded commitments related to private equity and real estate | 371 |  | 371 |  |
Private Equity Funds [Member] | ART [Member] |  |  |  |  |
Investment Gains (Losses) |  |  |  |  |
NDT unfunded commitments related to private equity and real estate | 142 |  | 142 |  |
Private Credit [Member] | NDT [Member] |  |  |  |  |
Investment Gains (Losses) |  |  |  |  |
NDT unfunded commitments related to private equity and real estate | 86 |  | 86 |  |
Private Credit [Member] | ART [Member] |  |  |  |  |
Investment Gains (Losses) |  |  |  |  |
NDT unfunded commitments related to private equity and real estate | $ 46 |  | $ 46 |  |

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