Contract with customer, asset and liability (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Jan. 01, 2018
Revenue from Contract with Customer [Abstract]
Contract with Customer, Asset, before Allowance for Credit Loss	$ 534.7	$ 523.5
change in contract asset	11.2
Contract with Customer, Liability	(514.6)	(527.7)
change in contract liability	13.1
Contract with Customer, Liability, Revenue Recognized	139.0
Contracts with Customers, Net Contract Asset (Liability)	20.1	$ (4.2)
change in net contract asset	$ 24.3