Revenues - Additional Information (Details) - ASC 2014-09 - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Jan. 01, 2018
Revenue Recognition [Line Items]
Increase in retained earnings		$ 1.9
Lease receivables	$ 7.8	10.9
Receivables from contract with customers	28.3	31.2
Future revenues under contract	700.4
Contracts currently being invoiced	$ 624.8
Average remaining contract term	2 years 10 months 24 days
Backlog for sales bookings	$ 75.6
Average remaining contract term of backlog sales bookings	4 years 3 months 18 days
General and Administrative Expense
Revenue Recognition [Line Items]
Impact of decrease in costs	$ (0.4)
Other Assets
Revenue Recognition [Line Items]
Deferred Costs	$ 2.9	$ 2.5