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Other Investments (Narrative) (Details) - RGC Midstream LLC [Member] Bcf in Millions, $ in Millions | 1 Months Ended |  |  |  |
--- | --- | --- | --- | --- | ---
Apr. 30, 2018 USD ($) mi | Mar. 31, 2020 USD ($) debt_instrument | Nov. 30, 2019 | Jun. 12, 2019 instrument_held | Oct. 31, 2015 Bcf
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Number of unsecured Promissory Notes funding the investment |  | 2 |  | 2 |
MVP [Member] |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Equity interest percentage |  |  | 1.03% |  | 1.00%
Pipeline capacity per day (in bcf) | Bcf |  |  |  |  | 2
MVP [Member] | Minimum [Member] |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Total project cost |  | $ 5,300.0 |  |  |
Total estimated investment |  | 55.0 |  |  |
MVP [Member] | Maximum [Member] |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Total project cost |  | 5,500.0 |  |  |
Total estimated investment |  | $ 57.0 |  |  |
Southgate [Member] |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Length of planned natural gas pipeline (in miles) | mi | 74 |  |  |  |
Estimated total MVP Southgate pipeline cost projection | $ 500.0 |  |  |  |
Estimated investment in MVP Southgate | $ 2.5 |  |  |  |
Southgate [Member] | Southgate [Member] |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Ownership percentage (less than) | 1.00% |  |  |  |

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