Inventories - Additional Information (Detail) bbl in Millions, $ in Millions	1 Months Ended	6 Months Ended	9 Months Ended
	Sep. 30, 2020 USD ($) vlcc bbl	Sep. 30, 2020 USD ($) vlcc bbl	Sep. 30, 2020 USD ($) vlcc bbl	Dec. 31, 2019 USD ($)
Inventory [Line Items]
Number of very large crude carriers | vlcc	3	3	3
Crude oil loaded in very large crude carriers (in barrels of oil) | bbl		6.3
Crude oil in very large crude carriers (in barrels of oil) | bbl	4.2	4.2	4.2
Cost of crude oil | $	$ 241	$ 241	$ 241	$ 92
Crude oil sold (in barrels of oil) | bbl	2.1
Charges related to inventories | $			53
Charges related to inventories, after income taxes | $			$ 52
Very Large Crude Carriers (VLCCs)
Inventory [Line Items]
Number of very large crude carriers | vlcc	3	3	3
Crude oil loaded in very large crude carriers (in barrels of oil) | bbl		6.3
Cost of crude oil | $	$ 147	$ 147	$ 147