Income Taxes Schedule of Deferred Tax Assets and Liabilities Footnotes (Details) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Income Taxes [Abstract]
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	$ 26	$ (27)

Amount of increase (decrease) in the valuation allowance for a specified deferred tax asset.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 45
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=84176650&loc=d3e32123-109318

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Balance Type:	credit
Period Type:	duration