Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Earnings Per Share [Abstract]
Net income	$ 569	$ 392	$ 381	$ 657	$ 722	$ 677	$ 1,342	$ 2,056
Dividend equivalent payments, basic	(2)			(1)			(3)	(4)
Dividend equivalent payments, diluted	(1)			0			(2)	0
Income available to common stockholders, basic	567			656			1,339	2,052
Income available to common stockholders, diluted	$ 568			$ 657			$ 1,340	$ 2,056
Weighted-average shares outstanding (in shares)	254.6			262.1			255.7	264.6
Dilutive effect of outstanding options and share-settled awards (in shares)	1.5			2.2			1.5	2.3
Adjusted weighted-average shares outstanding (in shares)	256.1			264.3			257.2	266.9
Basic (in dollars per share)	$ 2.23			$ 2.50			$ 5.24	$ 7.76
Diluted (in dollars per share)	$ 2.22			$ 2.49			$ 5.21	$ 7.70