Revenue Revenue (Narrative detail) (Details) $ in Millions	3 Months Ended
Mar. 31, 2018 USD ($)
Revenue Recognition and Deferred Revenue [Abstract]
Deferred Revenue, Revenue Recognized	$ 269.1

Amount of revenue recognized that was previously reported as deferred or unearned revenue.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 605
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 13.A.4(a).Q1 Response))
-URI http://asc.fasb.org/extlink&oid=65893310&loc=d3e214044-122780

Name:	us-gaap_DeferredRevenueRevenueRecognized1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration