Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Consolidated Statements of Comprehensive Income [Abstract]
Net income	$ 5,161	$ 5,481	$ 5,219
Other comprehensive income:
Change in pension and retiree health and welfare benefits, net of tax	(48)	16	(127)
Change in accumulated other comprehensive income (loss) of equity method investees	1	(1)	1
Other comprehensive income (loss), net of tax	(47)	15	(126)
Total comprehensive income	$ 5,114	$ 5,496	$ 5,093