Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 1,380	$ 1,305	$ 2,554	$ 2,522
Net actuarial losses of defined benefit plans:
Adjustments, net of tax effect of $4 and $2; $1 and $3	(10)	(3)	(1)	(5)
Recognized within net income, net of tax effect of ($3) and ($4); ($5) and ($7)	6	11	14	21
Available-for-sale investments:
Unrealized losses, net of tax effect of $0 and $0; $0 and $0	(2)	0	0	0
Other comprehensive income (loss), net of taxes	(6)	8	13	16
Total comprehensive income	$ 1,374	$ 1,313	$ 2,567	$ 2,538