Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 5,580	$ 3,682	$ 3,595
Net actuarial losses of defined benefit plans:
Adjustment, net of tax effect of $35, ($26) and $6	(98)	92	(43)
Recognized within net income, net of tax effect of ($15), ($27) and ($25)	50	56	51
Prior service credit of defined benefit plans:
Adjustment, net of tax effect of $1, $1 and $0	(6)	(2)	0
Recognized within net income, net of tax effect of $1, $1 and $2	(3)	(5)	(3)
Derivative instruments:
Change in fair value, net of tax effect of $1, $0 and $0	(2)	0	0
Recognized within net income, net of tax effect of $0, $0 and $0	0	1	1
Other comprehensive income (loss), net of taxes	(59)	142	6
Total comprehensive income	$ 5,521	$ 3,824	$ 3,601