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Equity (Cash Distributions Applicable to Period the Distributions Were Earned) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Class of Stock [Line Items] |  |  |
General partner's distributions on general partner units | $ 0 | $ 25 | $ 18
General partner's distributions on IDRs | 0 | 303 | 187
Total distribution on general partner units and IDRs | 0 | 328 | 205
Total cash distributions declared | 2,060 | 1,288 | 938
Limited Partners Common Units |  |  |
Class of Stock [Line Items] |  |  |
Limited partners' distributions | 1,985 | 895 | 692
Preferred Units |  |  |
Class of Stock [Line Items] |  |  |
Limited partners' distributions | $ 75 | $ 65 | $ 41

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