Acquisitions Acquisitions Narrative (Details) $ in Millions	6 Months Ended
Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)
Business Combinations [Abstract]
Goodwill and intangible assets related to acquisitions	$ 14.2	$ 22.9
Number of Businesses Acquired	2	3

Amount of liabilities assumed at the acquisition date.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=84161108&loc=d3e4845-128472

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