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, 2015		$ 22,172	$ 29,945	$ (157)	$ (28,362)
Shareholders' Equity [Rollforward]
Employee share-based compensation		123
Compensation amortization under share-based plans and other changes		124
Net income	$ 2,071		2,071
Dividends			(571)
Other			(2)
Other comprehensive income	817			817
Treasury stock acquired - share repurchase authorization					(1,650)
Net shares acquired related to employee share-based compensation plans					(71)
Shareholders' equity, end of period at Sep. 30, 2016	24,439	22,419	31,443	660	(30,083)
Balance, beginning of year (in shares) at Dec. 31, 2015						295.9
Common shares outstanding
Treasury stock acquired - share repurchase authorization (in shares)						(14.7)
Net shares issued under employee share-based compensation plans (in shares)						2.9
Balance, end of period (in shares) at Sep. 30, 2016						284.1
Shareholders' equity, beginning of year at Dec. 31, 2016	23,221	22,614	32,196	(755)	(30,834)
Shareholders' Equity [Rollforward]
Employee share-based compensation		118
Compensation amortization under share-based plans and other changes		104
Net income	1,505		1,505
Dividends			(591)
Other comprehensive income	470			470
Treasury stock acquired - share repurchase authorization	(1,028)				(1,028)
Net shares acquired related to employee share-based compensation plans	(61)				(61)
Shareholders' equity, end of period at Sep. 30, 2017	$ 23,738	$ 22,836	$ 33,110	$ (285)	$ (31,923)
Balance, beginning of year (in shares) at Dec. 31, 2016	279.6					279.6
Common shares outstanding
Treasury stock acquired - share repurchase authorization (in shares)	(8.3)					(8.3)
Net shares issued under employee share-based compensation plans (in shares)						2.4
Balance, end of period (in shares) at Sep. 30, 2017	273.7					273.7