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Related Party Transactions - Additional Information (Details) - shares
6 Months Ended
Jun. 30, 2019
Dec. 31, 2018
Jun. 30, 2019
Agreement To Transport Crude Oil On Pipeline Of Equity Method Investee | Equity Method Investee      
Related Party Transaction [Line Items]      
Ownership interest in unconsolidated entity 50.00%   50.00%
PAGP | Shares Class C      
Related Party Transaction [Line Items]      
Ownership interest (in units) 530,053,993 516,938,280  
Minimum | AAP | Principal Owner      
Related Party Transaction [Line Items]      
Limited partner interest     10.00%