Acquisitions (Details) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2017 USD ($)	Jun. 30, 2018 item	Jun. 30, 2017 USD ($)
Acquisitions
Number of acquisitions \| item		3
Acquisition-related expenses	$ 4.0		$ 4.0
Acquisition-related expenses, net of tax	$ 3.7

This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 23
-URI http://asc.fasb.org/extlink&oid=84229725&loc=d3e1043-128460

Name:	us-gaap_BusinessCombinationAcquisitionRelatedCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration