Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 5,595	$ 5,017	$ 5,580
Net actuarial losses of defined benefit plans:
Adjustments, net of tax effect of $3, ($37) and $35	(41)	88	(98)
Recognized within net income, net of tax effect of ($9), ($13) and ($15)	29	38	50
Prior service credit of defined benefit plans:
Adjustments, net of tax effect of $0, $0 and $1	0	0	(6)
Recognized within net income, net of tax effect of $0, $0 and $1	(1)	0	(3)
Derivative instruments:
Change in fair value, net of tax effect of $0, $1 and $0 - post adoption	0	0
Change in fair value, net of tax effect of $0, $1 and $0 - pre adoption			(2)
Other comprehensive income (loss), net of taxes	(13)	126	(59)
Total comprehensive income	$ 5,582	$ 5,143	$ 5,521