Net Income Per Share (Schedule of Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Denominator
Basic net income per share (in dollars per share)	$ 59.15	$ 49.59	$ 44.22
Weighted-average effect of dilutive securities
Diluted net income per share (in dollars per share)	$ 58.61	$ 49.16	$ 43.70
Class A Common Stock
Numerator
Allocation of undistributed earnings	$ 17,733	$ 14,846	$ 13,200
Denominator
Number of shares used in basic computation (in shares)	299,815	299,402	298,548
Basic net income per share (in dollars per share)	$ 59.15	$ 49.59	$ 44.22
Numerator
Allocation of undistributed earnings for basic computation	$ 17,733	$ 14,846	$ 13,200
Reallocation of undistributed earnings as a result of conversion of Class B to Class A shares	2,732	2,307	2,072
Reallocation of undistributed earnings	(180)	(126)	(146)
Allocation of undistributed earnings	$ 20,285	$ 17,027	$ 15,126
Denominator
Number of shares used in basic computation (in shares)	299,815	299,402	298,548
Weighted-average effect of dilutive securities
Conversion of Class B to Class A common shares outstanding (in shares)	46,182	46,527	46,864
Restricted stock units and other contingently issuable shares (in shares)	87	413	689
Number of shares used in per share computation (in shares)	346,084	346,342	346,101
Diluted net income per share (in dollars per share)	$ 58.61	$ 49.16	$ 43.70
Class B Common Stock
Numerator
Allocation of undistributed earnings	$ 2,732	$ 2,307	$ 2,072
Denominator
Number of shares used in basic computation (in shares)	46,182	46,527	46,864
Basic net income per share (in dollars per share)	$ 59.15	$ 49.59	$ 44.22
Numerator
Allocation of undistributed earnings for basic computation	$ 2,732	$ 2,307	$ 2,072
Reallocation of undistributed earnings as a result of conversion of Class B to Class A shares	0	0	0
Reallocation of undistributed earnings	(25)	(20)	(24)
Allocation of undistributed earnings	$ 2,707	$ 2,287	$ 2,048
Denominator
Number of shares used in basic computation (in shares)	46,182	46,527	46,864
Weighted-average effect of dilutive securities
Conversion of Class B to Class A common shares outstanding (in shares)	0	0	0
Restricted stock units and other contingently issuable shares (in shares)	0	0	0
Number of shares used in per share computation (in shares)	46,182	46,527	46,864
Diluted net income per share (in dollars per share)	$ 58.61	$ 49.16	$ 43.70
Class C Capital Stock
Numerator
Allocation of undistributed earnings	$ 19,804	$ 17,190	$ 15,464
Denominator
Number of shares used in basic computation (in shares)	334,819	346,667	349,728
Basic net income per share (in dollars per share)	$ 59.15	$ 49.59	$ 44.22
Numerator
Allocation of undistributed earnings for basic computation	$ 19,804	$ 17,190	$ 15,464
Reallocation of undistributed earnings as a result of conversion of Class B to Class A shares	0	0	0
Reallocation of undistributed earnings	180	126	146
Allocation of undistributed earnings	$ 19,984	$ 17,316	$ 15,610
Denominator
Number of shares used in basic computation (in shares)	334,819	346,667	349,728
Weighted-average effect of dilutive securities
Conversion of Class B to Class A common shares outstanding (in shares)	0	0	0
Restricted stock units and other contingently issuable shares (in shares)	6,125	5,547	7,456
Number of shares used in per share computation (in shares)	340,944	352,214	357,184
Diluted net income per share (in dollars per share)	$ 58.61	$ 49.16	$ 43.70