Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 5,017	$ 5,580	$ 3,682
Net actuarial losses of defined benefit plans:
Adjustments, net of tax effect of ($37), $35 and ($26)	88	(98)	92
Recognized within net income, net of tax effect of ($13), ($15) and ($27)	38	50	56
Prior service credit of defined benefit plans:
Adjustments, net of tax effect of $0, $1 and $1	0	(6)	(2)
Recognized within net income, net of tax effect of $0, $1 and $1	0	(3)	(5)
Derivative instruments:
Change in fair value, net of tax effect of $0, $1 and $0 - post adoption	0
Change in fair value, net of tax effect of $0, $1 and $0 - pre adoption		(2)	0
Recognized within net income, net of tax effect of $0, $0 and $0 - post adoption	0
Recognized within net income, net of tax effect of $0, $0 and $0 - pre adoption		0	1
Other comprehensive income (loss), net of taxes	126	(59)	142
Total comprehensive income	$ 5,143	$ 5,521	$ 3,824