Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 1,285	$ 1,018	$ 3,338	$ 2,548
Net actuarial gains (losses) of defined benefit plans:
Adjustments	(1)	(17)	(16)	(47)
Recognized within Net income	17	12	40	39
Prior service (cost) credit of defined benefit plans:
Adjustments	0	0	0	1
Recognized within Net income	(1)	(1)	(3)	(3)
Other comprehensive income (loss)	15	(6)	21	(10)
Total comprehensive income	$ 1,300	$ 1,012	$ 3,359	$ 2,538