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]
Shareholders' equity, beginning of year at Dec. 31, 2012		$ 21,161	$ 21,352	$ 2,236	$ (19,344)
Shareholders' Equity [Rollforward]
Employee share-based compensation		158
Compensation amortization under share-based plans and other changes		181
Net income	$ 3,673		3,673
Dividends			(734)
Other comprehensive income (loss)	(1,426)			(1,426)
Treasury stock acquired - share repurchase authorization					(2,400)
Net shares acquired related to employee share-based compensation plans					(61)
Shareholders' equity, end of year at Dec. 31, 2013	24,796	21,500	24,291	810	(21,805)
Balance, beginning of year at Dec. 31, 2012						377.4
Common shares outstanding
Treasury stock acquired - share repurchase authorization						(28.4)
Net shares issued under employee share-based compensation plans						4.5
Balance, end of year at Dec. 31, 2013						353.5
Shareholders' Equity [Rollforward]
Employee share-based compensation		149
Compensation amortization under share-based plans and other changes		194
Net income	3,692		3,692
Dividends			(735)
Other			3
Other comprehensive income (loss)	70			70
Treasury stock acquired - share repurchase authorization					(3,275)
Net shares acquired related to employee share-based compensation plans	(58)				(58)
Shareholders' equity, end of year at Dec. 31, 2014	$ 24,836	21,843	27,251	880	(25,138)
Common shares outstanding
Treasury stock acquired - share repurchase authorization						(35.1)
Net shares issued under employee share-based compensation plans						3.8
Balance, end of year at Dec. 31, 2014	322.2					322.2
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)				(3,150)
Net shares acquired related to employee share-based compensation plans	(74)				(74)
Shareholders' equity, end of year at Dec. 31, 2015	$ 23,598	$ 22,172	$ 29,945	$ (157)	$ (28,362)
Common shares outstanding
Treasury stock acquired - share repurchase authorization	(29.6)					(29.6)
Net shares issued under employee share-based compensation plans						3.3
Balance, end of year at Dec. 31, 2015	295.9					295.9