Summary Of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2016	Dec. 31, 2015
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Debt issuance costs	$ 49	$ 49	$ 57
Debt retirement payments	$ 82	82
Accounting Standards Update 2015-03 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Debt issuance costs			$ 81
Accounting Standards Update 2016-15 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Debt retirement payments		$ 82