Stockholders' Equity (Schedule of Treasury Stock) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended				143 Months Ended
	Dec. 31, 2019	Dec. 31, 2018		Dec. 31, 2017	Dec. 31, 2019
Stockholders' Equity Note [Abstract]
Shares reacquired under clawback agreement		1,700
Shares repurchased	9,166,267	7,933,692	[1]	5,436,803	56,878,978
Average purchase price per share	$ 109.10	$ 103.01		$ 91.97	$ 73.01
Amount spent on repurchased shares (in millions)	$ 1,000	$ 817		$ 500	$ 4,153
Aggregate Board of Directors repurchase authorizations during the period	1,500	$ 0		$ 1,500
Share repurchase plan, authorized repurchase amount	$ 5,366				$ 5,366

[1] Excludes 1,700 common shares reacquired pursuant to an employee clawback agreement.