Summary Of Significant Accounting Policies (Narrative) (Details) $ in Millions		3 Months Ended		9 Months Ended
	Jul. 10, 2017 shares	Sep. 30, 2017 USD ($) shares	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) segment item shares	Sep. 30, 2016 USD ($)	Jul. 09, 2017 shares	Dec. 31, 2016 shares
Summary Of Significant Accounting Policies [Abstract]
Number of reportable segments | segment				1
Reverse stock split, conversion ratio	0.0667
Common Stock, Shares Authorized	175,000,000	175,000,000		175,000,000		1,750,000,000	175,000,000
Common stock, shares issued (in shares)	80,000,000	79,532,000		79,532,000		1,193,000,000	79,532,000
Common stock, shares outstanding (in shares)	79,000,000	78,462,000		78,462,000		1,178,000,000	78,170,000
Reverse Stock Split, Fractional Shares Issued	0
Customer surcharges | $		$ 52	$ 60	$ 160	$ 161
Number of revenue categories | item				5
Number of operating segments | segment				1