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Related Party Transactions - Additional Information (Details) - shares
9 Months Ended
Sep. 30, 2019
Dec. 31, 2018
Sep. 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 shares) 546,897,362 516,938,280  
Minimum | AAP | Principal Owner      
Related Party Transaction [Line Items]      
Limited partner interest     10.00%