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Fair Value Measurements - Fair Value Measurements (Details) - USD ($) $ in Millions | Sep. 30, 2023 | Sep. 30, 2022
--- | --- | ---
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Fair value | $ 52 | $ 1 |
Investments |  |  |
Government debt securities | 347 | 332 |
Corporate debt securities | 300 | 282 |
Mortgage and asset-backed securities | 36 | 52 |
Institutional mutual funds | 288 | 242 |
Forward debt securities contracts - asset | 11 | 4 |
Cash, Cash Equivalents, and Short-term Investments | 270 | 179 |
Private equity funds measured at net asset value | 583 | 487 |
Private real estate measured at net asset value | 387 | 369 |
Private credit measured at net asset value | 158 | 103 |
Commingled funds measured at net asset value | 1,135 | 1,087 |
Total investments | 4,123 | 3,671 |
Interest Rate Derivative Assets, at Fair Value | 4 |  |
Commodity contract derivatives | 33 | 152 |
Total | 4,160 | 3,946 |
Liabilities |  |  |
Currency swaps | 141 | 240 | [1]
Interest rate swaps | 662 | 905 |
Commodity contract derivatives | 2 | 7 |
Total | 991 | 1,160 |
Equity Securities, FV-NI, Noncurrent | 608 | 534 |
Derivative Liability, Subject to Master Netting Arrangement, after Offset | 991 | 1,160 |
Derivative Asset, Subject to Master Netting Arrangement, after Offset | 37 | 275 |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |
Cash, Cash Equivalents, and Short-term Investments | 270 | 179 |
Government debt securities reclassed |  | 1 |
Corporate debt securities reclassed |  | 1 |
Commingled funds reclassed |  | 116 |
Commodity Contract under FHP |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Fair value | (186) | 115 |
Liabilities |  |  |
Derivative Liability, Subject to Master Netting Arrangement, after Offset | 186 | 8 |
Derivative Asset, Subject to Master Netting Arrangement, after Offset | 0 | 123 |
Fair Value, Inputs, Level 1 |  |  |
Investments |  |  |
Government debt securities | 287 | 297 |
Corporate debt securities | 0 | 0 |
Mortgage and asset-backed securities | 0 | 0 |
Institutional mutual funds | 288 | 242 |
Forward debt securities contracts - asset | 0 | 0 |
Cash, Cash Equivalents, and Short-term Investments | 104 | 61 |
Private equity funds measured at net asset value | 0 | 0 |
Private real estate measured at net asset value | 0 | 0 |
Private credit measured at net asset value | 0 | 0 |
Commingled funds measured at net asset value | 0 | 0 |
Total investments | 1,287 | 1,134 |
Interest Rate Derivative Assets, at Fair Value | 0 |  |
Commodity contract derivatives | 0 | 0 |
Total | 1,287 | 1,134 |
Liabilities |  |  |
Currency swaps | 0 | 0 |
Interest rate swaps | 0 | 0 |
Commodity contract derivatives | 0 | 0 |
Total | 0 | 0 |
Equity Securities, FV-NI, Noncurrent | 608 | 534 |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |
Cash, Cash Equivalents, and Short-term Investments | 104 | 61 |
Fair Value, Inputs, Level 1 | Commodity Contract under FHP |  |  |
Liabilities |  |  |
Derivative Liability, Subject to Master Netting Arrangement, after Offset | 0 | 0 |
Derivative Asset, Subject to Master Netting Arrangement, after Offset |  | 0 |
Fair Value, Inputs, Level 2 |  |  |
Investments |  |  |
Government debt securities | 60 | 35 |
Corporate debt securities | 300 | 282 |
Mortgage and asset-backed securities | 36 | 52 |
Institutional mutual funds | 0 | 0 |
Forward debt securities contracts - asset | 11 | 4 |
Cash, Cash Equivalents, and Short-term Investments | 166 | 118 |
Private equity funds measured at net asset value | 0 | 0 |
Private real estate measured at net asset value | 0 | 0 |
Private credit measured at net asset value | 0 | 0 |
Commingled funds measured at net asset value | 0 | 0 |
Total investments | 573 | 491 |
Interest Rate Derivative Assets, at Fair Value | 4 |  |
Commodity contract derivatives | 33 | 152 |
Total | 610 | 766 |
Liabilities |  |  |
Currency swaps | 141 | 240 |
Interest rate swaps | 662 | 905 |
Commodity contract derivatives | 2 | 7 |
Total | 991 | 1,160 |
Equity Securities, FV-NI, Noncurrent | 0 | 0 |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |
Cash, Cash Equivalents, and Short-term Investments | 166 | 118 |
Fair Value, Inputs, Level 2 | Commodity Contract under FHP |  |  |
Liabilities |  |  |
Derivative Liability, Subject to Master Netting Arrangement, after Offset | 186 | 8 |
Derivative Asset, Subject to Master Netting Arrangement, after Offset |  | 123 |
Fair Value, Inputs, Level 3 |  |  |
Investments |  |  |
Government debt securities | 0 | 0 |
Corporate debt securities | 0 | 0 |
Mortgage and asset-backed securities | 0 | 0 |
Institutional mutual funds | 0 | 0 |
Forward debt securities contracts - asset | 0 | 0 |
Cash, Cash Equivalents, and Short-term Investments | 0 | 0 |
Private equity funds measured at net asset value | 0 | 0 |
Private real estate measured at net asset value | 0 | 0 |
Private credit measured at net asset value | 0 | 0 |
Commingled funds measured at net asset value | 0 | 0 |
Total investments | 0 | 0 |
Interest Rate Derivative Assets, at Fair Value | 0 |  |
Commodity contract derivatives | 0 | 0 |
Total | 0 | 0 |
Liabilities |  |  |
Currency swaps | 0 | 0 |
Interest rate swaps | 0 | 0 |
Commodity contract derivatives | 0 | 0 |
Total | 0 | 0 |
Equity Securities, FV-NI, Noncurrent | 0 | 0 |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |
Cash, Cash Equivalents, and Short-term Investments | 0 | 0 |
Fair Value, Inputs, Level 3 | Commodity Contract under FHP |  |  |
Liabilities |  |  |
Derivative Liability, Subject to Master Netting Arrangement, after Offset | $ 0 | 0 |
Derivative Asset, Subject to Master Netting Arrangement, after Offset |  | $ 0 |
[1] | See Note 15 — Risk Management Activities and Derivative Transactions — Offsetting of Derivative Assets and Liabilities.

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- Definition Cash includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the customer may deposit additional funds at any time and effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid Investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months. Short-term investments, exclusive of cash equivalents, generally consist of marketable securities intended to be sold within one year (or the normal operating cycle if longer) and may include trading securities, available-for-sale securities, or held-to-maturity securities (if maturing within one year), as applicable. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(9)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1 + Details
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