Revenue From Contracts With Customers - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Jan. 01, 2018
Disaggregation of Revenue [Line Items]
Extended payment terms granted, minimum period to adjust contract consideration for the time value of money	1 year
Contract assets	$ 0.9
Contract liabilities	20.3	$ 21.4
Revenue recognized	8.6
Deferred contract costs	84.2
Amortization of deferred contract costs	8.9
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-01-01
Disaggregation of Revenue [Line Items]
Unsatisfied performance obligations	426.0
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Disaggregation of Revenue [Line Items]
Unsatisfied performance obligations	444.0
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Disaggregation of Revenue [Line Items]
Unsatisfied performance obligations	676.3
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Disaggregation of Revenue [Line Items]
Unsatisfied performance obligations	$ 1,500.0