Contract with customer, asset and liability (Details) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 27, 2018	Sep. 27, 2018	Jan. 01, 2018
Revenue from Contract with Customer [Abstract]
Contract with Customer, Liability, Revenue Recognized	$ 40,100,000.0
Contract with Customer, Asset, Gross	566,700,000	$ 566,700,000	$ 517,800,000
Change in contract asset		48,900,000
Contract with Customer, Liability	(507,300,000)	(507,300,000)	(319,400,000)
Change in contract liability		(187,900,000)
Contract with Customer, Asset, Net	$ 59,400,000	59,400,000	$ 198,400,000
Change in net contract asset		$ (139,000,000)