Supplemental Cash Flow Information - Supplemental Cash Flow Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Supplemental Cash Flow Information:
Interest paid	$ 399	$ 421	$ 398
Income taxes paid, net of refunds	$ 209	$ 215	$ 211