Stockholders' Equity (Schedule of Treasury Stock) (Details) - USD ($) $ / shares in Units, $ in Millions		9 Months Ended		149 Months Ended
	Jul. 15, 2020	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2020
Class of Stock [Line Items]
Shares repurchased		2,770,321	7,334,433	59,649,299
Average purchase price per share		$ 94.44	$ 105.67	$ 74.00
Shares repurchased (in $ millions)		$ 261	$ 775	$ 4,414
Aggregate Board of Directors repurchase authorizations (in $ millions)	$ 500	$ 500	$ 1,500	$ 5,866