Fair value measurements - level 3 roll (Details) (Contingent Consideration Classified as Equity [Member], Fair Value, Inputs, Level 3 [Member], USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Dec. 27, 2014	Dec. 28, 2013	Dec. 27, 2014	Dec. 28, 2013	Sep. 27, 2014	Jun. 28, 2014	Sep. 28, 2013	Jun. 29, 2013
Contingent Consideration Classified as Equity [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value	$ 12.4	$ 17.3	$ 12.4	$ 17.3	$ 12.4	$ 17.4	$ 22.2	$ 22.2
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0	(4.9)	0	(4.9)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements	$ 0	$ 0	$ (5.0)	$ 0