Commitments And Contingencies Lease Guarantees (Details) $ in Millions	12 Months Ended
Dec. 31, 2017 USD ($)
Guarantor Obligations [Line Items]
Maximum potential undiscounted rental payments	$ 20.3
Loss Contingency Accrual, Payments	$ 0.0
Property Lease Guarantee [Member]
Guarantor Obligations [Line Items]
Property Leases	27
Performance Guarantee [Member]
Guarantor Obligations [Line Items]
Property Leases	5

Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248

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