Summary Of Significant Accounting Policies (Narrative) (Details) $ in Millions	3 Months Ended
Mar. 31, 2017 USD ($) segment	Mar. 31, 2016 USD ($)
Summary Of Significant Accounting Policies [Abstract]
Number of reportable segments \| segment	1
Customer surcharges \| $	$ 53	$ 39

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

No definition available.

Name:	us-gaap_NumberOfReportableSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration