Revenue - Method of Adoption (Details) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2017 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Three months ended December 31, 2018			$ 0.4
2019			1.5
2020			1.5
2021			1.5
2022			1.6
Thereafter			23.3
Total			29.8
Adjustment to revenue and cost of services and products for adoption of ASC 606	$ 33.6	$ 96.8
Capitalized Contract Cost, Net, Incremental Assets Related to Fulfillment and Acquisition Costs						$ 32.3
Capitalized Contract Cost, Net			$ 33.7	$ 32.5	$ 32.4	$ 32.4
Revenue, Remaining Performance Obligation, Percentage			80.00%
Indefeasible Right of Use, Maximum, in Years			30