General Goodwill (Details) $ in Millions	9 Months Ended
Sep. 30, 2018 USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill, Period Increase (Decrease)	$ 209

Amount of increase (decrease) of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=108376223&loc=d3e13816-109267

Name:	us-gaap_GoodwillPeriodIncreaseDecrease
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration