Goodwill & Other Intangible Assets Finite-Lived Intangible Assets (Details) $ in Millions	3 Months Ended
Mar. 31, 2018 USD ($)
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Cost Incurred to Renew or Extend	$ 46
Finite-Lived Intangible Asset, Weighted Average Period before Next Renewal or Extension	10 years

Weighted average period before the next renewal or extension (both explicit and implicit) for intangible assets that have been renewed or extended, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (d)(2)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

Name:	us-gaap_FiniteLivedIntangibleAssetWeightedAveragePeriodBeforeNextRenewalOrExtension
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration