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Investments Accounted for by the Equity Method and Variable Interest Entities - Summary of Equity Method Investments (Details) - USD ($) $ in Millions | Dec. 31, 2017 | Dec. 31, 2016
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Investments Accounted for by the Equity Method |  |
Equity investments in affiliates | $ 1,038 | $ 1,120
Undistributed earnings by equity investment | $ 120 | $ 101
GenConn |  |
Investments Accounted for by the Equity Method |  |
Economic interest in equity method investments (as a percent) | 50.00% |
Equity investments in affiliates | $ 102 |
Gladstone Power Station |  |
Investments Accounted for by the Equity Method |  |
Economic interest in equity method investments (as a percent) | 37.50% |
Equity investments in affiliates | $ 139 |
United States | Avenal Solar Holdings LLC |  |
Investments Accounted for by the Equity Method |  |
Economic interest in equity method investments (as a percent) | 50.00% |
Equity investments in affiliates | $ (6) |
United States | Desert Sunlight |  |
Investments Accounted for by the Equity Method |  |
Economic interest in equity method investments (as a percent) | 25.00% |
Equity investments in affiliates | $ 272 |
United States | Elkhorn Ridge Wind, LLC |  |
Investments Accounted for by the Equity Method |  |
Economic interest in equity method investments (as a percent) | 47.00% |
Equity investments in affiliates | $ 73 |
United States | GenConn |  |
Investments Accounted for by the Equity Method |  |
Economic interest in equity method investments (as a percent) | 50.00% |
Equity investments in affiliates | $ 102 |
United States | Four Brothers Holdings |  |
Investments Accounted for by the Equity Method |  |
Economic interest in equity method investments (as a percent) | 50.00% |
Equity investments in affiliates | $ 213 |
United States | Granite Mountain Renewables |  |
Investments Accounted for by the Equity Method |  |
Economic interest in equity method investments (as a percent) | 50.00% |
Equity investments in affiliates | $ 78 |
United States | Iron Springs Renewables |  |
Investments Accounted for by the Equity Method |  |
Economic interest in equity method investments (as a percent) | 50.00% |
Equity investments in affiliates | $ 54 |
United States | Midway-Sunset Cogeneration Company |  |
Investments Accounted for by the Equity Method |  |
Economic interest in equity method investments (as a percent) | 50.00% |
Equity investments in affiliates | $ 16 |
United States | San Juan Mesa Wind Project, LLC |  |
Investments Accounted for by the Equity Method |  |
Economic interest in equity method investments (as a percent) | 75.00% |
Equity investments in affiliates | $ 66 |
United States | Watson Cogeneration Company |  |
Investments Accounted for by the Equity Method |  |
Economic interest in equity method investments (as a percent) | 49.00% |
Equity investments in affiliates | $ 21 |
United States | Various |  |
Investments Accounted for by the Equity Method |  |
Equity investments in affiliates | $ 10 |
Australia | Gladstone Power Station |  |
Investments Accounted for by the Equity Method |  |
Economic interest in equity method investments (as a percent) | 37.50% |
Equity investments in affiliates | $ 139 |
Mechanically-complete Solar Assets | Sun Edison Utility-Scale Solar and Wind |  |
Investments Accounted for by the Equity Method |  |
Equity investments in affiliates | $ 345 |

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