Schedule of Net Periodic Benefit Costs (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Sep. 26, 2014	Sep. 27, 2013	Sep. 28, 2012
Defined Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 4.1	$ 4.8	$ 4.3
Interest cost	6.1	5.2	5.3
Loss due to settlement or curtailment	1.8	1.0	0.9
Expected return on assets	(7.8)	(5.7)	(5.3)
Amortization of prior service cost	0.2	0.2	0.2
Recognized actuarial loss	2.1	2.7	2.5
Net periodic benefit cost	6.5	8.2	7.9
New prior service (credit) cost		0.5
Net (gain) loss arising during the year	10.3	(6.6)	9.9
Amortization of prior service cost	(0.2)	(0.2)	(0.2)
Amortization, settlement and curtailment of net actuarial loss	(3.9)	(3.7)	(3.5)
Total recognized in other comprehensive (income) loss	6.2	(10.0)	6.2
Total recognized in net periodic benefit cost and other comprehensive (income) loss	12.7	(1.8)	14.1
Post-Retirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Interest cost	0.2	0.2	0.2
Recognized actuarial loss			0.1
Net periodic benefit cost	0.2	0.2	0.3
New prior service (credit) cost	(3.3)
Net (gain) loss arising during the year	0.2	(0.4)	(0.1)
Amortization, settlement and curtailment of net actuarial loss		(0.1)	(0.1)
Total recognized in other comprehensive (income) loss	(3.1)	(0.5)	(0.2)
Total recognized in net periodic benefit cost and other comprehensive (income) loss	$ (2.9)	$ (0.3)	$ 0.1