Revenue Recognition - Narrative (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($) service payment	Mar. 31, 2017 USD ($)
Revenue from External Customer [Line Items]
Revenue recognized that was included in the contract liability balance at the beginning of the period	$ 48.8	$ 19.5
Revenue recognized, advance billings	$ 47.8	19.5
Base fees, number of monthly payments | payment	3
Number of distinct services, allocation of variable payments (or more) | service	1
Revenue recognized from changes in transaction prices	$ 0.0	$ 1.4
End-To-End Contracts | Minimum
Revenue from External Customer [Line Items]
Contract length	3 years
End-To-End Contracts | Maximum
Revenue from External Customer [Line Items]
Contract length	10 years
PAS and Modular Agreements | Minimum
Revenue from External Customer [Line Items]
Contract length	1 year
PAS and Modular Agreements | Maximum
Revenue from External Customer [Line Items]
Contract length	3 years
PAS
Revenue from External Customer [Line Items]
Revenue performance obligation, period (often less than)	1 day