Derivatives (Hedges of Net Investments in Foreign Operations) (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivatives used in Net Investment Hedge, Net of Tax	$ 178	$ 184

Amount, after tax, of cumulative translation adjustment attributable to gain (loss) on foreign currency derivatives that are designated as, and are effective as, economic hedges of a net investment in a foreign entity.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 830
-SubTopic 30
-Section 45
-Paragraph 20
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109240241&loc=d3e32211-110900

Name:	us-gaap_TranslationAdjustmentForNetInvestmentHedgeNetOfTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant