Supplemental Cash Flow Information - Summary of Supplemental Cash Flow Information (Detail) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Net cash provided by operating activities included:
Interest paid (net of amounts capitalized)	$ 423	$ 402
Income Taxes Paid, Net	1	0
Non-cash investing and financing activities:
Net transfers of property, plant and equipment (to)/from materials and supplies inventories	$ (1)	$ 1