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Fair Value Measurements Fair Value Measurements - Investments (Details) $ in Millions | 3 Months Ended |
--- | --- | ---
Dec. 31, 2022 USD ($) Units | Dec. 31, 2021 USD ($) | Sep. 30, 2022 USD ($)
Investment Gains (Losses) |  |  |
Financing Receivable, after Allowance for Credit Loss | $ 100 |  | $ 96
Balance in NDT | $ 2,700 |  |
Period of time where the investor contributes capital to an investment in a private partnership - minimum | Units | 3 |  |
Period of time where the investor contributes capital to an investment in a private partnership - maximum | Units | 4 |  |
Minimum investment period | Units | 10 |  |
Number of readily available quoted exchange prices for the investments | 0 |  |
Investment funds | $ 3,913 |  | 3,671
Affiliated Entity |  |  |
Investment Gains (Losses) |  |  |
Investment funds | 402 |  | $ 358
SERP |  |  |
Investment Gains (Losses) |  |  |
Unrealized gains (losses) on investments | (3) | $ (2) |
ART [Member] |  |  |
Investment Gains (Losses) |  |  |
Unrealized gains (losses) on investments | (69) | (30) |
NDT [Member] |  |  |
Investment Gains (Losses) |  |  |
Unrealized gains (losses) on investments | 136 | $ (119) |
Equity Funds |  |  |
Investment Gains (Losses) |  |  |
NDT unfunded commitments related to private equity and real estate | 179 |  |
Real Estate Funds |  |  |
Investment Gains (Losses) |  |  |
NDT unfunded commitments related to private equity and real estate | 118 |  |
Credit [Member] |  |  |
Investment Gains (Losses) |  |  |
NDT unfunded commitments related to private equity and real estate | 80 |  |
Private Equity Funds [Member] |  |  |
Investment Gains (Losses) |  |  |
NDT unfunded commitments related to private equity and real estate | 95 |  |
Private real estate funds [Member] |  |  |
Investment Gains (Losses) |  |  |
Fair value plan assets gross | 67 |  |
Private Credit [Member] |  |  |
Investment Gains (Losses) |  |  |
NDT unfunded commitments related to private equity and real estate | $ 42 |  |

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- Definition Assets, usually stocks, bonds, and other investments, that have been segregated and restricted (usually in a trust) to provide benefits, at their fair value as of the measurement date. Plan assets include amounts contributed by the employer (and by employees for a contributory plan) and amounts earned from investing the contributions, less benefits paid. This amount is not reduced by non-benefit liabilities. + References No definition available. + Details
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