Equity (Aggregate Share Repurchases) (Details) - USD ($) shares in Millions, $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Equity, Class of Treasury Stock [Line Items]
Cash consideration	$ 5,320	$ 5,435	$ 5,352
New Authorization [Member]
Equity, Class of Treasury Stock [Line Items]
Cash consideration	$ 5,000	$ 5,000	$ 5,000
Shares repurchased (in shares)	140	131	161

Number of shares that have been repurchased and retired during the period.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
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Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration