Revenue from Contracts with Customers - Performance Obligations, Narrative (Details) $ in Millions	6 Months Ended
Jun. 30, 2018 USD ($)
Disaggregation of Revenue [Line Items]
Variable consideration, percentage constrained	100.00%
Unsatisfied performance obligation	$ 441.8
Minimum
Disaggregation of Revenue [Line Items]
Payment terms	0 days
Maximum
Disaggregation of Revenue [Line Items]
Payment terms	30 days

Amount of transaction price allocated to performance obligation that has not been recognized as revenue.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 270
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=84173487&loc=SL51747714-108306

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=82913847&loc=SL49130556-203045

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