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Consolidated Balance Sheets (Parenthetical) - shares shares in Millions | Jun. 30, 2017 | Dec. 31, 2016
--- | --- | ---
Limited Partners Common Units [Member] | Public |  |
Units issued | 284 | 271
Units outstanding | 284 | 271
Limited Partners Class B Units |  |
Units issued | 4 | 4
Units outstanding | 4 | 4
MPC | Limited Partners Common Units [Member] |  |
Units issued | 90 | 86
Units outstanding | 90 | 86
MPC | GP Held Limited Partners Common Units |  |
Units issued | 9 | 0
Units outstanding | 9 | 0
MPC | General Partner |  |
GP units issued | 8 | 7
GP units outstanding | 8 | 7

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