Equity (Changes in Common Stock) (Details) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Class A Common Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock, shares outstanding at beginning of period (in shares)	4,516,518,147	4,635,000,000	4,742,000,000
Stock compensation plans (in shares)	21,000,000	15,000,000	19,000,000
Repurchases and retirements of common stock (in shares)	0	(140,000,000)	(131,000,000)
Employee stock purchase plan (in shares)	6,000,000	7,000,000	5,000,000
Common stock, shares outstanding at end of period (in shares)	4,543,590,270	4,516,518,147	4,635,000,000
Class B Common Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock, shares outstanding at beginning of period (in shares)	9,444,375	9,000,000	9,000,000
Stock compensation plans (in shares)	0	0	0
Repurchases and retirements of common stock (in shares)	0	0	0
Employee stock purchase plan (in shares)	0	0	0
Common stock, shares outstanding at end of period (in shares)	9,444,375	9,444,375	9,000,000