Summary Of Business And Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Discontinued operation, equity method investment retained after disposal, ownership interest after disposal	20.50%
Equity earnings (loss), net of taxes		$ 177	$ 198	$ 117