Noncontrolling interests (Details) - USD ($) $ in Millions		9 Months Ended
	Apr. 28, 2016	Sep. 30, 2016	Sep. 25, 2015
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Noncontrolling interests, beginning		$ 42.9	$ 40.0
Purchase of noncontrolling interest		(19.5)	0.0
Net income attributable to noncontrolling interests		2.0	4.5
Translation adjustments		0.3	(1.1)
Retirement benefit adjustment		(0.1)	(0.1)
Capital contributions from, net		0.3	0.1
Noncontrolling interests, ending		$ 25.9	$ 43.4
Variable Interest Entity [Member]
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Payments to acquire remaining interest in VIE	$ 45.0
Liabilities incurred to purchase remaining interest	25.5
Noncontrolling interest in variable interest entity	$ 19.5