Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 1,366	$ 997
Net actuarial losses of defined benefit plans:
Adjustments	(16)	(12)
Recognized within Net income	9	12
Prior service credit of defined benefit plans:
Recognized within Net income	(1)	(1)
Other comprehensive income (loss)	(8)	(1)
Total comprehensive income	$ 1,358	$ 996