Consolidated Statement of Changes in Equity - USD ($) $ in Millions	Total	Common Stock Class A	Common Stock Class B	Additional Paid-In Capital	Class A Treasury Stock	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Non- Controlling Interests
Balance at beginning of period at Dec. 31, 2017	$ 5,497	$ 0	$ 0	$ 4,365	$ (20,764)	$ 22,364	$ (497)	$ 29
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,492					1,492
Activity related to non-controlling interests	(1)							(1)
Other comprehensive income, net of tax	124						124
Cash dividends declared on Class A and Class B common stock	(262)					(262)
Purchases of treasury stock	(1,383)				(1,383)
Share-based payments	6			2	4
Balance at end of period at Mar. 31, 2018	5,656	0	0	4,367	(22,143)	23,777	(373)	28
Balance at beginning of period at Dec. 31, 2017	5,497	0	0	4,365	(20,764)	22,364	(497)	29
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	4,960
Other comprehensive income, net of tax	(173)
Balance at end of period at Sep. 30, 2018	5,796	0	0	4,526	(24,807)	26,726	(670)	21
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of new accounting principle | Adoption of revenue standard	366					366
Adoption of new accounting principle | Adoption of intra-entity asset transfers standard	(183)					(183)
Balance at beginning of period at Mar. 31, 2018	5,656	0	0	4,367	(22,143)	23,777	(373)	28
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,569					1,569
Activity related to non-controlling interests	(6)							(6)
Other comprehensive income, net of tax	(259)						(259)
Cash dividends declared on Class A and Class B common stock	(260)					(260)
Purchases of treasury stock	(1,507)				(1,507)
Share-based payments	86			86	0
Balance at end of period at Jun. 30, 2018	5,279	0	0	4,453	(23,650)	25,086	(632)	22
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,899					1,899
Activity related to non-controlling interests	(1)							(1)
Other comprehensive income, net of tax	(38)						(38)
Cash dividends declared on Class A and Class B common stock	(259)					(259)
Purchases of treasury stock	(1,158)				(1,158)
Share-based payments	74			73	1
Balance at end of period at Sep. 30, 2018	5,796	0	0	4,526	(24,807)	26,726	(670)	21
Balance at beginning of period at Dec. 31, 2018	5,418	0	0	4,580	(25,750)	27,283	(718)	23
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,862					1,862
Activity related to non-controlling interests	(1)							(1)
Other comprehensive income, net of tax	45						45
Cash dividends declared on Class A and Class B common stock	(339)					(339)
Purchases of treasury stock	(1,790)				(1,790)
Share-based payments	(5)			(11)	6
Balance at end of period at Mar. 31, 2019	5,190	0	0	4,569	(27,534)	28,806	(673)	22
Balance at beginning of period at Dec. 31, 2018	5,418	0	0	4,580	(25,750)	27,283	(718)	23
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	6,018					6,018
Other comprehensive income, net of tax	(140)
Balance at end of period at Sep. 30, 2019	4,975	0	0	4,725	(31,207)	32,289	(858)	26
Balance at beginning of period at Mar. 31, 2019	5,190	0	0	4,569	(27,534)	28,806	(673)	22
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	2,048					2,048
Activity related to non-controlling interests	5							5
Other comprehensive income, net of tax	(57)						(57)
Cash dividends declared on Class A and Class B common stock	(337)					(337)
Purchases of treasury stock	(1,920)				(1,920)
Share-based payments	106			106	0
Balance at end of period at Jun. 30, 2019	5,035	0	0	4,675	(29,454)	30,517	(730)	27
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	2,108					2,108
Activity related to non-controlling interests	(1)							(1)
Other comprehensive income, net of tax	(128)						(128)
Cash dividends declared on Class A and Class B common stock	(336)					(336)
Purchases of treasury stock	(1,755)				(1,755)
Share-based payments	52			50	2
Balance at end of period at Sep. 30, 2019	$ 4,975	$ 0	$ 0	$ 4,725	$ (31,207)	$ 32,289	$ (858)	$ 26