Supplemental Cash Flow Information - Reconciliation of Additions to Property, Plant and Equipment to Total Capital Expenditures (Detail) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Supplemental Cash Flow Elements [Abstract]
Additions to property, plant and equipment per the consolidated statements of cash flows				$ 2,419	$ 1,466
Asset retirement expenditures				0	5
Increase (decrease) in capital accruals				(281)	77
Capital expenditures	[1]	$ 1,132	$ 841	$ 2,138	$ 1,548

[1] Capital expenditures include changes in capital accruals. See Note 19 for a reconciliation of total capital expenditures to additions to property, plant and equipment for the six months ended June 30, 2019 and 2018 as reported in the consolidated statements of cash flows.