Consolidated Statements 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]
Shareholders' equity, beginning of year at Dec. 31, 2014		$ 21,843	$ 27,251	$ 880	$ (25,138)
Shareholders' Equity [Rollforward]
Employee share-based compensation		133
Compensation amortization under share-based plans and other changes		196
Net income	$ 3,439		3,439
Dividends			(744)
Other			(1)
Other comprehensive income (loss)	(1,037)			(1,037)
Treasury stock acquired - share repurchase authorization					(3,150)
Net shares acquired related to employee share-based compensation plans					(74)
Shareholders' equity, end of year at Dec. 31, 2015	23,598	22,172	29,945	(157)	(28,362)
Balance, beginning of year (in shares) at Dec. 31, 2014						322.2
Common shares outstanding
Treasury stock acquired - share repurchase authorization (in shares)						(29.6)
Net shares issued under employee share-based compensation plans (in shares)						3.3
Balance, end of year (in shares) at Dec. 31, 2015						295.9
Shareholders' Equity [Rollforward]
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)				(72)
Shareholders' equity, end of year at Dec. 31, 2016	$ 23,221	22,614	32,196	(755)	(30,834)
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					279.6
Shareholders' Equity [Rollforward]
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)				(1,378)
Net shares acquired related to employee share-based compensation plans	(62)				(62)
Shareholders' equity, 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)					(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