Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Earnings Per Share [Abstract]
Shareholders' net income	$ 813	$ 510	$ 1,411	$ 1,029
Shares:
Weighted average	254,087,000	255,381,000	254,879,000	255,101,000
Common stock equivalents	3,974,000	4,119,000	4,034,000	4,372,000
Total shares	258,061,000	259,500,000	258,913,000	259,473,000
EPS, basic	$ 3.2	$ 2	$ 5.54	$ 4.03
EPS, effect of dilution	(0.05)	(0.03)	(0.09)	(0.06)
EPS, diluted	$ 3.15	$ 1.97	$ 5.45	$ 3.97
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common shares held in Treasury	43,286,059	39,587,801	43,286,059	39,587,801
Employee Stock Option [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive options	1,200,000	2,600,000	1,900,000	2,000,000