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Investments in Unconsolidated Affiliates (Gas Utilities and Infrastructure Investments) (Details) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2020
Investments In Unconsolidated Affiliates [Line Items] |  |  |
Investments in equity method unconsolidated affiliates | $ 1,936 | $ 1,409 | $ 961
Gas Utilities and Infrastructure |  |  |
Investments In Unconsolidated Affiliates [Line Items] |  |  |
Investments in equity method unconsolidated affiliates | 1,388 | 1,003 | $ 215
Gas Utilities and Infrastructure | ACP |  |  |
Investments In Unconsolidated Affiliates [Line Items] |  |  |
Ownership interest |  |  | 47.00%
Investments in equity method unconsolidated affiliates | 1,179 |  |
Gas Utilities and Infrastructure | Sabal Trail |  |  |
Investments In Unconsolidated Affiliates [Line Items] |  |  |
Ownership interest |  |  | 7.50%
Investments in equity method unconsolidated affiliates | 121 |  | $ 120
Gas Utilities and Infrastructure | Other |  |  |
Investments In Unconsolidated Affiliates [Line Items] |  |  |
Ownership interest |  |  | 29.68%
Investments in equity method unconsolidated affiliates |  |  | $ 3
Gas Utilities and Infrastructure | Constitution |  |  |
Investments In Unconsolidated Affiliates [Line Items] |  |  |
Ownership interest |  |  | 24.00%
Impairment losses | 25 | $ 55 |
Piedmont and Duke | Gas Utilities and Infrastructure | Cardinal |  |  |
Investments In Unconsolidated Affiliates [Line Items] |  |  |
Ownership interest |  |  | 21.49%
Investments in equity method unconsolidated affiliates | 9 |  | $ 9
Piedmont and Duke | Gas Utilities and Infrastructure | Pine Needle |  |  |
Investments In Unconsolidated Affiliates [Line Items] |  |  |
Ownership interest |  |  | 45.00%
Investments in equity method unconsolidated affiliates | 28 |  | $ 27
Piedmont and Duke | Gas Utilities and Infrastructure | Hardy Storage |  |  |
Investments In Unconsolidated Affiliates [Line Items] |  |  |
Ownership interest |  |  | 50.00%
Investments in equity method unconsolidated affiliates | $ 51 |  | $ 56

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- Definition This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=109237563&loc=d3e33749-111570 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 25 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8813-108599 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.12) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
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