Capital Transactions - Dividends (Details) - USD ($) $ / shares in Units, $ in Millions					9 Months Ended
May 09, 2018	Feb. 01, 2018	May 10, 2017	Feb. 02, 2017	Sep. 30, 2018	Sep. 30, 2017
Dividends
Dividends per common share (in dollars per share)		$ 0.34		$ 0.30	$ 0.34
Cash dividend payment	$ 259		$ 226		$ 259	$ 226

Aggregate dividends declared during the period for each share of common stock outstanding.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

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Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration