Sales - Contract liabilities (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 25, 2020	Sep. 25, 2020	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Deferred revenue - current	$ 85.1	$ 85.1	$ 87.0
Deferred revenue - noncurrent	57.9	57.9	63.2
Total contract liabilities	143.0	143.0	$ 150.2
Contract liabilities, revenue recognized	$ 31.1	$ 84.8