Consolidated Statement of Changes in Shareholders' Equity - USD ($) shares in Millions, $ in Millions	Total	Common stock [Member]	Retained earnings [Member]	Accumulated other comprehensive income (loss), net of tax [Member]	Treasury stock, at cost [Member]	Common shares outstanding [Member]
Balance, beginning of year at Dec. 31, 2015		$ 22,172	$ 29,945	$ (157)	$ (28,362)
Shareholders' Equity [Roll Forward]
Employee share-based compensation		287
Compensation amortization under share-based plans and other changes		155
Net income	$ 3,014		3,014
Dividends			(762)
Other			(1)
Other comprehensive income (loss)	(598)			(598)
Treasury stock acquired — share repurchase authorization					(2,400)
Net shares acquired related to employee share-based compensation plans					(72)
Balance, end of year at Dec. 31, 2016	23,221	22,614	32,196	(755)	(30,834)
Balance, beginning of year (in shares) at Dec. 31, 2015						295.9
Common shares outstanding
Treasury stock acquired — share repurchase authorization (in shares)						(21.3)
Net shares issued under employee share-based compensation plans (in shares)						5.0
Balance, end of year (in shares) at Dec. 31, 2016						279.6
Shareholders' Equity [Roll Forward]
Employee share-based compensation		136
Compensation amortization under share-based plans and other changes		136
Net income	2,056		2,056
Dividends			(789)
Other			(1)
Other comprehensive income (loss)	412			412
Treasury stock acquired — share repurchase authorization					(1,378)
Net shares acquired related to employee share-based compensation plans	(62)				(62)
Balance, end of year at Dec. 31, 2017	$ 23,731	22,886	33,462	(343)	(32,274)
Common shares outstanding
Treasury stock acquired — share repurchase authorization (in shares)						(10.9)
Net shares issued under employee share-based compensation plans (in shares)						2.7
Balance, end of year (in shares) at Dec. 31, 2017	271.4					271.4
Shareholders' Equity [Roll Forward]
Reclassification of certain tax effects from adoption of updated accounting guidance				(24)
Cumulative effect of adoption of updated accounting guidance for equity financial instruments			22	(22)
Balance, beginning of year at Dec. 31, 2017	$ 23,731	22,886	33,462	(343)	(32,274)
Shareholders' Equity [Roll Forward]
Employee share-based compensation		108
Compensation amortization under share-based plans and other changes		150
Reclassification of certain tax effects from adoption of updated accounting guidance			24	(24)
Net income	2,523		2,523
Dividends			(818)
Other			(9)
Other comprehensive income (loss)	(1,470)			(1,470)
Treasury stock acquired — share repurchase authorization	(1,270)				(1,270)
Net shares acquired related to employee share-based compensation plans	(51)				(51)
Balance, end of year at Dec. 31, 2018	$ 22,894	$ 23,144	$ 35,204	(1,859)	$ (33,595)
Balance, beginning of year (in shares) at Dec. 31, 2017	271.4					271.4
Common shares outstanding
Treasury stock acquired — share repurchase authorization (in shares)	(9.6)					(9.6)
Net shares issued under employee share-based compensation plans (in shares)						1.8
Balance, end of year (in shares) at Dec. 31, 2018	263.6					263.6
Shareholders' Equity [Roll Forward]
Cumulative effect of adoption of updated accounting guidance for equity financial instruments				$ (22)