Derivative Financial Instruments (Narrative) (Details) $ in Millions	3 Months Ended
Mar. 31, 2019 USD ($)
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Cash flow hedge gains (losses) expected to be reclassified to earnings within the next 12 months	$ 9
Cash flow hedge ineffectiveness is immaterial	Hedge ineffectiveness was immaterial for all periods presented.

The estimated net amount of existing gains or losses on cash flow hedges at the reporting date expected to be reclassified to earnings within the next 12 months.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=112277219&loc=d3e80748-113994

Name:	us-gaap_CashFlowHedgeGainLossToBeReclassifiedWithinTwelveMonths
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration