Equity (Common Stock) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	12 Months Ended
Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Dividends Payable [Line Items]
Dividend Aggregate													$ 1,678	$ 1,717	$ 1,736
Common stock
Dividends Payable [Line Items]
Declaration Date	Oct. 23, 2018	Jul. 06, 2018	Apr. 24, 2018	Jan. 05, 2018	Oct. 24, 2017	Jul. 07, 2017	Apr. 25, 2017	Jan. 06, 2017	Oct. 25, 2016	Jul. 07, 2016	Apr. 26, 2016	Jan. 06, 2016
Record Date	Nov. 06, 2018	Aug. 06, 2018	May 07, 2018	Feb. 05, 2018	Nov. 06, 2017	Aug. 07, 2017	May 08, 2017	Feb. 06, 2017	Nov. 07, 2016	Aug. 08, 2016	May 09, 2016	Feb. 05, 2016
Payment Date	Dec. 13, 2018	Sep. 13, 2018	Jun. 13, 2018	Mar. 13, 2018	Dec. 13, 2017	Sep. 13, 2017	Jun. 13, 2017	Mar. 13, 2017	Dec. 13, 2016	Sep. 13, 2016	Jun. 13, 2016	Mar. 14, 2016
Dividend Per Share	$ 0.42	$ 0.42	$ 0.42	$ 0.400	$ 0.4	$ 0.400	$ 0.400	$ 0.400	$ 0.400	$ 0.400	$ 0.400	$ 0.375	$ 1.66	$ 1.6	$ 1.575
Dividend Aggregate	$ 415	$ 419	$ 428	$ 416	$ 422	$ 427	$ 431	$ 437	$ 441	$ 441	$ 441	$ 413	$ 1,678	$ 1,717	$ 1,736

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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
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-Paragraph 1
-Subparagraph (SX 210.3-04)
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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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