Commitments And Contingencies (Narrative) (Details) $ in Millions	12 Months Ended
Dec. 31, 2017 USD ($)
Commitments and Contingencies [Abstract]
Standby letters of credit extension period, in years	1 year
Accrued settlement payment	$ 10

Amount of loss contingency liability.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14326-108349

Name:	us-gaap_LossContingencyAccrualAtCarryingValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant