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	$ 456.7	$ 456.7	$ 410.1
Deferred revenue - noncurrent	90.5	90.5	99.2
Total contract liabilities	547.2	547.2	$ 509.3
Contract liabilities, revenue recognized	$ 104.0	$ 314.0