Segment Information - Revenues by Product Line (Details) - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Revenue from External Customer [Line Items]    
Sales and other operating revenues [1] $ 18,694 $ 16,134
Refined products    
Revenue from External Customer [Line Items]    
Sales and other operating revenues 16,158 13,876
Merchandise    
Revenue from External Customer [Line Items]    
Sales and other operating revenues 1,130 1,192
Crude oil and refinery feedstocks    
Revenue from External Customer [Line Items]    
Sales and other operating revenues 883 687
Service, transportation and other    
Revenue from External Customer [Line Items]    
Sales and other operating revenues $ 523 $ 379
[1] The 2018 period reflects an election to present certain taxes on a net basis. See Notes 2 and 3 for further information.