Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 1,570	$ 1,285	$ 4,341	$ 3,338
Net actuarial losses of defined benefit plans:
Adjustments	3	(1)	2	(16)
Recognized within Net income	15	17	33	40
Prior service credit of defined benefit plans:
Recognized within Net income	(1)	(1)	(3)	(3)
Derivative instruments:
Change in fair value	0	0	(2)	0
Other comprehensive income (loss)	17	15	30	21
Total comprehensive income	$ 1,587	$ 1,300	$ 4,371	$ 3,359