Condensed Consolidated Statement of Changes in Equity (Unaudited) - USD ($) $ in Millions	Total	Redeemable Noncontrolling Interests and Redeemable Subsidiary Preferred Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Retained Earnings [Member] Cumulative Effect, Period of Adoption, Adjustment [Member]	Treasury Stock at Cost [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interest [Member]	Class A Common Stock [Member] Common Stock [Member]
Beginning balance at Dec. 31, 2019		$ 1,372
Increase (Decrease) in Temporary Equity [Roll Forward]
Redemption of subsidiary preferred stock		0
Contributions from (distributions to) noncontrolling interests, net		(46)
Other		(174)
Net income (loss)		102
Ending balance at Sep. 30, 2020		1,254
Beginning balance at Dec. 31, 2019			$ 38,447	$ 50,695	$ (124)	$ (7,517)	$ 1,047	$ 1,148	$ 54
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock compensation plans			713
Issuances of common stock under employee plans									0
Repurchases of common stock under repurchase program and employee plans			(164)	(281)
Employee stock purchase plans			193
Dividends declared				(3,187)
Other comprehensive income (loss)							(835)	14
Contributions from (distributions to) noncontrolling interests, net								200
Other			(16)	(3)				25
Net income (loss)	$ 7,154			7,154
Net income (loss)								8
Ending balance at Sep. 30, 2020	$ 87,571		39,173	54,254		(7,517)	212	1,395	54
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends declared per common share (in dollars per share)	$ 0.69
Beginning balance at Jun. 30, 2020		1,256
Increase (Decrease) in Temporary Equity [Roll Forward]
Redemption of subsidiary preferred stock		0
Contributions from (distributions to) noncontrolling interests, net		(9)
Other		(9)
Net income (loss)		16
Ending balance at Sep. 30, 2020		1,254
Beginning balance at Jun. 30, 2020			38,936	53,420	0	(7,517)	(1,279)	1,177	54
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock compensation plans			240
Issuances of common stock under employee plans									0
Repurchases of common stock under repurchase program and employee plans			(61)	(113)
Employee stock purchase plans			60
Dividends declared				(1,062)
Other comprehensive income (loss)							1,491	38
Contributions from (distributions to) noncontrolling interests, net								185
Other			(2)	(10)				(1)
Net income (loss)	$ 2,019			2,019
Net income (loss)								(4)
Ending balance at Sep. 30, 2020	$ 87,571		39,173	54,254		(7,517)	212	1,395	54
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends declared per common share (in dollars per share)	$ 0.23
Beginning balance at Dec. 31, 2020	$ 1,280	1,280
Increase (Decrease) in Temporary Equity [Roll Forward]
Redemption of subsidiary preferred stock		(725)
Contributions from (distributions to) noncontrolling interests, net		(59)
Other		(10)
Net income (loss)		33
Ending balance at Sep. 30, 2021	520	520
Beginning balance at Dec. 31, 2020	91,738		39,464	56,438	0	(7,517)	1,884	1,415	54
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock compensation plans			802
Issuances of common stock under employee plans									0
Repurchases of common stock under repurchase program and employee plans			(340)	(2,290)
Employee stock purchase plans			201
Dividends declared				(3,470)
Other comprehensive income (loss)							(556)	11
Contributions from (distributions to) noncontrolling interests, net								379
Other			7	4				0
Net income (loss)	11,102			11,102
Net income (loss)								(282)
Ending balance at Sep. 30, 2021	$ 97,306		40,134	61,783		(7,517)	1,328	1,524	54
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends declared per common share (in dollars per share)	$ 0.75
Beginning balance at Jun. 30, 2021		530
Increase (Decrease) in Temporary Equity [Roll Forward]
Redemption of subsidiary preferred stock		0
Contributions from (distributions to) noncontrolling interests, net		(19)
Other		0
Net income (loss)		9
Ending balance at Sep. 30, 2021	$ 520	$ 520
Beginning balance at Jun. 30, 2021			40,046	60,359	$ 0	(7,517)	1,992	1,581	55
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock compensation plans			233
Issuances of common stock under employee plans									0
Repurchases of common stock under repurchase program and employee plans			(209)	(1,458)
Employee stock purchase plans			62
Dividends declared				(1,153)
Other comprehensive income (loss)							(664)	2
Contributions from (distributions to) noncontrolling interests, net								55
Other			2	0				(2)
Net income (loss)	4,035			4,035
Net income (loss)								(112)
Ending balance at Sep. 30, 2021	$ 97,306		$ 40,134	$ 61,783		$ (7,517)	$ 1,328	$ 1,524	$ 54
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends declared per common share (in dollars per share)	$ 0.25