Consolidated Statement of Changes in Shareholders' Equity (Unaudited) - USD ($) shares in Millions, $ in Millions	Total	Common stock [Member]	Retained earnings [Member]	Retained earnings [Member] Cumulative Effect, Period of Adoption, Adjustment [Member]	Accumulated other comprehensive income (loss), net of tax [Member]	Treasury stock, at cost [Member]	Common shares outstanding [Member]
Shareholders' Equity [Roll Forward]
Shareholders' equity		$ 23,469	$ 36,977	$ (43)	$ 640	$ (35,143)
Balance, beginning of period at Dec. 31, 2019		23,469	36,977	(43)	640	(35,143)
Shareholders' Equity [Roll Forward]
Employee share-based compensation		27
Compensation amortization under share-based plans and other changes		46
Shareholders' equity	$ 25,204	23,542	37,325	$ (43)	(49)	(35,614)
Net income	600		600
Dividends			(210)
Other			1
Other comprehensive loss	(689)				(689)
Treasury stock acquired — share repurchase authorization						(425)
Net shares acquired related to employee share-based compensation plans						(46)
Balance, end of period at Mar. 31, 2020	25,204	23,542	37,325		(49)	(35,614)
Balance, beginning of year (in shares) at Dec. 31, 2019							255.5
Common shares outstanding
Treasury stock acquired - share repurchase authorization (in shares)							(3.5)
Net shares issued under employee share-based compensation plans (in shares)							0.8
Balance, end of period (in shares) at Mar. 31, 2020							252.8
Shareholders' Equity [Roll Forward]
Shareholders' equity	25,204	23,542	37,325		(49)	(35,614)
Shareholders' equity	29,201	23,743	38,771		2,502	(35,815)
Balance, beginning of period at Dec. 31, 2020	29,201	23,743	38,771		2,502	(35,815)
Shareholders' Equity [Roll Forward]
Employee share-based compensation		108
Compensation amortization under share-based plans and other changes		54
Shareholders' equity	29,201	23,905	39,285		2,502	(36,212)
Net income	733		733
Dividends			(216)
Other			(3)
Other comprehensive loss	(1,211)				(1,211)
Treasury stock acquired — share repurchase authorization	(356)					(356)
Net shares acquired related to employee share-based compensation plans	(41)					(41)
Balance, end of period at Mar. 31, 2021	$ 28,269	23,905	39,285		1,291	(36,212)
Balance, beginning of year (in shares) at Dec. 31, 2020	252.4						252.4
Common shares outstanding
Treasury stock acquired - share repurchase authorization (in shares)	(2.4)						(2.4)
Net shares issued under employee share-based compensation plans (in shares)							1.5
Balance, end of period (in shares) at Mar. 31, 2021	251.5						251.5
Shareholders' Equity [Roll Forward]
Shareholders' equity	$ 28,269	$ 23,905	$ 39,285		$ 1,291	$ (36,212)