Consolidated Statement of Changes in Shareholders' Equity (Unaudited) - USD ($) shares in Millions, $ in Millions	Total	Common stock [Member]	Retained earnings [Member]	Accumulated other comprehensive loss, net of tax [Member]	Treasury stock, at cost [Member]	Common shares outstanding [Member]
Shareholders' Equity [Roll Forward]
Cumulative effect of adoption of updated accounting guidance for equity financial instruments			$ 22	$ (22)
Balance, beginning of year at Dec. 31, 2017		$ 22,886	33,462	(343)	$ (32,274)
Shareholders' Equity [Roll Forward]
Employee share-based compensation		65
Compensation amortization under share-based plans and other changes		44
Reclassification of certain tax effects from adoption of updated accounting guidance			24	(24)
Net income	$ 669		669
Dividends			(197)
Other			1
Other comprehensive income (loss)	(933)			(933)
Treasury stock acquired — share repurchase authorization					(350)
Net shares acquired related to employee share-based compensation plans					(51)
Balance, end of period at Mar. 31, 2018	22,979	22,995	33,981	(1,322)	(32,675)
Balance, beginning of year (in shares) at Dec. 31, 2017						271.4
Common shares outstanding
Treasury stock acquired - share repurchase authorization (in shares)						(2.5)
Net shares issued under employee share-based compensation plans (in shares)						1.3
Balance, end of period (in shares) at Mar. 31, 2018						270.2
Balance, beginning of year at Dec. 31, 2018	22,894	23,144	35,204	(1,859)	(33,595)
Shareholders' Equity [Roll Forward]
Employee share-based compensation		54
Compensation amortization under share-based plans and other changes		45
Net income	796		796
Dividends			(204)
Other			(1)
Other comprehensive income (loss)	1,177			1,177
Treasury stock acquired — share repurchase authorization	(375)				(375)
Net shares acquired related to employee share-based compensation plans	(46)				(46)
Balance, end of period at Mar. 31, 2019	$ 24,340	$ 23,243	$ 35,795	$ (682)	$ (34,016)
Balance, beginning of year (in shares) at Dec. 31, 2018	263.6					263.6
Common shares outstanding
Treasury stock acquired - share repurchase authorization (in shares)	(2.9)					(2.9)
Net shares issued under employee share-based compensation plans (in shares)						1.2
Balance, end of period (in shares) at Mar. 31, 2019	261.9					261.9