Sales to Related Parties (Detail) - USD ($) $ in Millions		3 Months Ended			6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019		Jun. 30, 2020	Jun. 30, 2019
Related Party Transaction [Line Items]
Rental income - related parties		$ 237	$ 286	[1]	$ 471	$ 611	[1]
Other income - related parties		63	27	[1]	127	53	[1]
MPC
Related Party Transaction [Line Items]
Rental income - related parties		237	286		471	611
Other income - related parties		48	10		96	20
Product sales to MPC that net to zero		52	295		225	518
Other Affiliates [Member]
Related Party Transaction [Line Items]
Other income - related parties		15	17		31	33
Product [Member]
Related Party Transaction [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		30	36	[1],[2]	63	77	[1],[2]
Product [Member] | MPC
Related Party Transaction [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties	[3]	30	36		63	77
Service [Member]
Related Party Transaction [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		857	847	[1],[2]	1,785	1,650	[1],[2]
Service [Member] | MPC
Related Party Transaction [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		857	847		1,784	1,650
Service [Member] | Other Affiliates [Member]
Related Party Transaction [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		$ 0	$ 0		$ 1	$ 0

[1] Financial information for the three and six months ended June 30, 2019 has been retrospectively adjusted for the acquisition of ANDX. See Notes 1 and 3.

[2] Financial information for the three and six months ended June 30, 2019 has been retrospectively adjusted for the acquisition of ANDX. See Notes 1 and 3.

[3] There were additional product sales to MPC that net to zero within the consolidated financial statements as the transactions are recorded net due to the terms of the agreements under which such product was sold. For the three and six months ended June 30, 2020, these sales totaled $52 million and $225 million. For the three and six months ended June 30, 2019, these sales totaled $295 million and $518 million.