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Fair Value Measurements Fair Value Measurements - Investments (Details) $ in Millions | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Mar. 31, 2019 USD ($) | Mar. 31, 2018 USD ($) | Mar. 31, 2019 USD ($) | Mar. 31, 2018 USD ($) | Sep. 30, 2018 USD ($)
Investment Gains (Losses) |  |  |  |  |
Debt Securities, Trading, and Equity Securities, FV-NI | $ 2,835 |  | $ 2,835 |  |
Financing Receivable, Net | 136 |  | 136 |  | $ 123
Balance in NDT | 2,100 |  | 2,100 |  |
Balance in ART | $ 698 |  | $ 698 |  |
Period of time where the investor contributes capital to an investment in a private partnership - minimum |  |  | three |  |
Period of time where the investor contributes capital to an investment in a private partnership - maximum |  |  | four |  |
Minimum investment period |  |  | 10 years |  |
Number of readily available quoted exchange prices for the investments | 0 |  | 0 |  |
SERP |  |  |  |  |
Investment Gains (Losses) |  |  |  |  |
Unrealized gains (losses) on investments | $ 5 | $ (2) | $ (1) | $ 0 |
DCP |  |  |  |  |
Investment Gains (Losses) |  |  |  |  |
Unrealized gains (losses) on investments | 1 | (1) | (2) | 0 |
NDT |  |  |  |  |
Investment Gains (Losses) |  |  |  |  |
Unrealized gains (losses) on investments | 154 | (75) | (47) | (29) |
ART |  |  |  |  |
Investment Gains (Losses) |  |  |  |  |
Unrealized gains (losses) on investments | 52 | $ (14) | (52) | $ 6 |
Equity Funds |  |  |  |  |
Investment Gains (Losses) |  |  |  |  |
NDT unfunded commitments related to private equity and real estate | 142 |  | 142 |  |
Real Estate Funds |  |  |  |  |
Investment Gains (Losses) |  |  |  |  |
NDT unfunded commitments related to private equity and real estate | 26 |  | 26 |  |
Credit [Member] |  |  |  |  |
Investment Gains (Losses) |  |  |  |  |
NDT unfunded commitments related to private equity and real estate | 11 |  | 11 |  |
Private Equity Funds [Member] |  |  |  |  |
Investment Gains (Losses) |  |  |  |  |
NDT unfunded commitments related to private equity and real estate | 59 |  | 59 |  |
Private real estate funds [Member] |  |  |  |  |
Investment Gains (Losses) |  |  |  |  |
Fair value plan assets gross | 11 |  | 11 |  |
Private Credit [Member] |  |  |  |  |
Investment Gains (Losses) |  |  |  |  |
NDT unfunded commitments related to private equity and real estate | $ 6 |  | $ 6 |  |

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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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- Definition The fair value of investments held in a trust fund to pay for the costs of decontaminating and decommissioning nuclear facilities. + References No definition available. + Details
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- Definition Fair value portion of arrangements with third parties, including, but not limited to, operating lease arrangement and arrangement in which the entity has agreed to expend funds to procure goods or services, or has agreed to commit resources to supply goods or services. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(25)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Net amount of the investment in a contractual right to receive money on demand or on fixed or determinable dates that is recognized as an asset in the creditor's statement of financial position. Examples include, but are not limited to, credit card receivables, notes receivable and receivables relating to lessor's rights to payments from leases other than operating leases that have been recorded as assets. Excludes trade accounts receivable with contractual maturity of one year or less and arose from the sale of goods or services. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.3) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of investments, not including unrealized gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity, held at each balance sheet date and included in earnings for the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585 + Details
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