Consolidated Statement of Changes in Shareholders' Equity (Unaudited) - 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		66
Compensation amortization under share-based plans and other changes		73
Net income	$ 833		833
Dividends			(178)
Other comprehensive income (loss)	(111)			(111)
Treasury stock acquired - share repurchase authorization					(600)
Net shares acquired related to employee share-based compensation plans					(72)
Shareholders' equity, end of period at Mar. 31, 2015	24,847	21,982	27,906	769	(25,810)
Balance, beginning of year at Dec. 31, 2014						322.2
Common shares outstanding
Treasury stock acquired - share repurchase authorization						(5.6)
Net shares issued under employee share-based compensation plans						2.1
Balance, end of period at Mar. 31, 2015						318.7
Shareholders' equity, beginning of year at Dec. 31, 2015	23,598	22,172	29,945	(157)	(28,362)
Shareholders' Equity [Rollforward]
Employee share-based compensation		47
Compensation amortization under share-based plans and other changes		50
Net income	691		691
Dividends			(181)
Other			(1)
Other comprehensive income (loss)	571			571
Treasury stock acquired - share repurchase authorization	(550)				(550)
Net shares acquired related to employee share-based compensation plans	(59)				(59)
Shareholders' equity, end of period at Mar. 31, 2016	$ 24,166	$ 22,269	$ 30,454	$ 414	$ (28,971)
Balance, beginning of year at Dec. 31, 2015	295.9					295.9
Common shares outstanding
Treasury stock acquired - share repurchase authorization	(5.1)					(5.1)
Net shares issued under employee share-based compensation plans						1.6
Balance, end of period at Mar. 31, 2016	292.4					292.4