Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Denominator
Basic net income per share (in dollars per share)	$ 9.71	$ 7.36	$ 22.65	$ 20.59
Weighted-average effect of dilutive securities
Diluted net income per share (in dollars per share)	$ 9.57	$ 7.25	$ 22.30	$ 20.26
Class A Common Stock
Numerator
Allocation of undistributed earnings	$ 2,891	$ 2,171	$ 6,734	$ 6,047
Denominator
Number of shares used in basic computation (shares)	297,804	294,945	297,291	293,723
Basic net income per share (in dollars per share)	$ 9.71	$ 7.36	$ 22.65	$ 20.59
Numerator
Allocation of undistributed earnings for basic computation	$ 2,891	$ 2,171	$ 6,734	$ 6,047
Reallocation of undistributed earnings as a result of conversion of Class B to Class A shares	457	357	1,069	1,013
Reallocation of undistributed earnings	(38)	(25)	(92)	(68)
Allocation of undistributed earnings	$ 3,310	$ 2,503	$ 7,711	$ 6,992
Denominator
Number of shares used in basic computation (shares)	297,804	294,945	297,291	293,723
Weighted-average effect of dilutive securities
Conversion of Class B to Class A common shares outstanding (shares)	47,078	48,513	47,189	49,214
Number of shares used in per share computation (shares)	345,952	345,381	345,735	345,141
Diluted net income per share (in dollars per share)	$ 9.57	$ 7.25	$ 22.30	$ 20.26
Class A Common Stock \| Restricted stock units and other contingently issuable shares
Weighted-average effect of dilutive securities
Restricted stock units and other contingently issuable shares (shares)	1,070	1,923	1,255	2,204
Class B Common Stock
Numerator
Allocation of undistributed earnings	$ 457	$ 357	$ 1,069	$ 1,013
Denominator
Number of shares used in basic computation (shares)	47,078	48,513	47,189	49,214
Basic net income per share (in dollars per share)	$ 9.71	$ 7.36	$ 22.65	$ 20.59
Numerator
Allocation of undistributed earnings for basic computation	$ 457	$ 357	$ 1,069	$ 1,013
Reallocation of undistributed earnings as a result of conversion of Class B to Class A shares	0	0	0	0
Reallocation of undistributed earnings	(7)	(5)	(17)	(16)
Allocation of undistributed earnings	$ 450	$ 352	$ 1,052	$ 997
Denominator
Number of shares used in basic computation (shares)	47,078	48,513	47,189	49,214
Weighted-average effect of dilutive securities
Conversion of Class B to Class A common shares outstanding (shares)	0	0	0	0
Number of shares used in per share computation (shares)	47,078	48,513	47,189	49,214
Diluted net income per share (in dollars per share)	$ 9.57	$ 7.25	$ 22.30	$ 20.26
Class B Common Stock \| Restricted stock units and other contingently issuable shares
Weighted-average effect of dilutive securities
Restricted stock units and other contingently issuable shares (shares)	0	0	0	0
Class C Capital Stock
Numerator
Allocation of undistributed earnings	$ 3,384	$ 2,533	$ 7,879	$ 7,085
Denominator
Number of shares used in basic computation (shares)	348,603	344,103	347,853	344,162
Basic net income per share (in dollars per share)	$ 9.71	$ 7.36	$ 22.65	$ 20.59
Numerator
Allocation of undistributed earnings for basic computation	$ 3,384	$ 2,533	$ 7,879	$ 7,085
Reallocation of undistributed earnings as a result of conversion of Class B to Class A shares	0	0	0	0
Reallocation of undistributed earnings	38	25	92	68
Allocation of undistributed earnings	$ 3,422	$ 2,558	$ 7,971	$ 7,153
Denominator
Number of shares used in basic computation (shares)	348,603	344,103	347,853	344,162
Weighted-average effect of dilutive securities
Conversion of Class B to Class A common shares outstanding (shares)	0	0	0	0
Number of shares used in per share computation (shares)	357,764	353,059	357,350	353,058
Diluted net income per share (in dollars per share)	$ 9.57	$ 7.25	$ 22.30	$ 20.26
Class C Capital Stock \| Restricted stock units and other contingently issuable shares
Weighted-average effect of dilutive securities
Restricted stock units and other contingently issuable shares (shares)	9,161	8,956	9,497	8,896

Dilutive impact on our earnings per share for the period as a result of conversion of Class B to Class A common stock.

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Reallocation of undistributed earnings to Class B shares.

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The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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