Property and Equipment	9 Months Ended
Sep. 30, 2018
Property, Plant and Equipment [Abstract]
Property and Equipment	Property and Equipment Property and equipment are net of accumulated depreciation of $329.6 million and $306.2 million at September 30, 2018 and December 31, 2017, respectively.

The entire disclosure for long-lived, physical assets used in the normal conduct of business and not intended for resale. Includes, but is not limited to, accounting policies and methodology, roll forwards, depreciation, depletion and amortization expense, including composite depreciation, accumulated depreciation, depletion and amortization expense, useful lives and method used, income statement disclosures, assets held for sale and public utility disclosures.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-URI http://asc.fasb.org/topic&trid=2155823

Name:	us-gaap_PropertyPlantAndEquipmentDisclosureTextBlock
Namespace Prefix:	us-gaap_
Data Type:	nonnum:textBlockItemType
Balance Type:	na
Period Type:	duration