Revenue Recogniton Revenue Recognition (Details) $ in Millions	12 Months Ended
Dec. 31, 2018 USD ($)
Revenue Recognition [Abstract]
Gain on Derivative Instruments, Pretax	$ 42

Aggregate gain on all derivative instruments recognized in earnings during the period, before tax effects.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5618551-113959

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