Revenue - Schedule of contract liabilities (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018
Change in Contract with Customer, Liability [Roll Forward]
Balance at beginning of period	$ 71.4	$ 62.8
Additional advanced billings and deposits received	88.9	188.2
Revenue recognized	(94.6)	(184.9)
Foreign currency translation adjustments and other	(2.8)	(3.2)
Balance at end of period	$ 62.9	$ 62.9