Revenues - Narrative (Details) $ in Millions	6 Months Ended
	Jun. 30, 2018 USD ($) segment
Deferred Revenue Arrangement [Line Items]
Number of reportable segments | segment	2
Contract with customer, liability, revenue recognized in the period	$ 10.3
Deferred revenue, noncurrent recognition period	4 years
Remaining performance obligation	$ 92.0
Difference between Revenue Guidance in Effect before and after Topic 606
Deferred Revenue Arrangement [Line Items]
Decrease in deferred revenue	$ 3.2