Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 1,174	$ 1,217
Net actuarial losses of defined benefit plans:
Adjustments, net of tax effect of ($3) and $1	9	(2)
Recognized within net income, net of tax effect of ($2) and ($3)	8	10
Available-for-sale investments:
Unrealized gains, net of tax effect of $0 and $0	2	0
Other comprehensive income (loss), net of taxes	19	8
Total comprehensive income	$ 1,193	$ 1,225