Impairment (Detail) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2020 USD ($)	Mar. 31, 2020 USD ($) $ / bbl	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)
Impairments [Line Items]
Impairment charge, pre-tax	$ 0		$ 0	$ 2,126	$ 0
Oil and Gas Properties
Impairments [Line Items]
Fair value of estimated impairment charges determined using internal projected discounted cash flows		$ 1,050
Weighted average crude oil benchmark price for impaired assets (US dollar per barrel) | $ / bbl		48.82
Discount rate used in fair value measurements		10.00%
Oil and Gas Properties | West Texas Intermediate
Impairments [Line Items]
Future strip crude oil price (US dollar per barrel) used in impairment | $ / bbl		50
Oil and Gas Properties | Brent
Impairments [Line Items]
Future strip crude oil price (US dollar per barrel) used in impairment | $ / bbl		55
Oil and Gas Properties | North Malay Basin Field | Malaysia
Impairments [Line Items]
Impairment charge, pre-tax				755
Impairment charge, after income taxes				755
Oil and Gas Properties | South Arne Field | Denmark
Impairments [Line Items]
Impairment charge, pre-tax				670
Impairment charge, after income taxes				594
Oil and Gas Properties | Stampede Field | Gulf of Mexico
Impairments [Line Items]
Impairment charge, pre-tax				410
Impairment charge, after income taxes				410
Oil and Gas Properties | Tubular Bells Field | Gulf of Mexico
Impairments [Line Items]
Impairment charge, pre-tax				270
Impairment charge, after income taxes				270
Other Assets
Impairments [Line Items]
Impairment charge, pre-tax				21
Impairment charge, after income taxes				$ 20