Other Intangible Assets - Finite-Lived Intangible Assets (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Mar. 31, 2018	Sep. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Finite-lived Intangible Assets Acquired	$ 46
Finite-Lived Intangible Asset, Useful Life		10 years

Amount of increase in assets, excluding financial assets, lacking physical substance with a definite life, from an acquisition.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16265-109275

Name:	us-gaap_FinitelivedIntangibleAssetsAcquired1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration