Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 1,405	$ 1,056	$ 2,771	$ 2,053
Net actuarial losses of defined benefit plans:
Adjustments	15	(3)	(1)	(15)
Recognized within Net income	9	11	18	23
Prior service credit of defined benefit plans:
Recognized within Net income	(1)	(1)	(2)	(2)
Derivative instruments:
Change in fair value	(2)	0	(2)	0
Other comprehensive income (loss)	21	7	13	6
Total comprehensive income	$ 1,426	$ 1,063	$ 2,784	$ 2,059