Retirement Plans - Schedule of Net Periodic Benefit Costs (Detail) - Defined Benefit Plans - USD ($) $ in Millions	12 Months Ended
	Sep. 29, 2017	Sep. 30, 2016	Oct. 02, 2015
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 7.1	$ 5.9	$ 5.6
Interest cost	2.4	4.0	4.4
Loss due to settlement	1.4	1.0	1.1
Expected return on assets	(7.1)	(6.7)	(7.1)
Amortization of prior service cost	(0.5)	0.0	0.1
Recognized actuarial loss	4.3	2.9	2.4
Net periodic benefit cost	7.6	7.1	6.5
New prior service credit	(5.0)	(1.2)	(1.1)
Net (gain) loss arising during the year	(12.2)	25.3	6.7
Amortization of prior service credit (cost)	0.5	0.0	(0.1)
Amortization or settlement of net actuarial loss	(5.7)	(3.9)	(3.5)
Total recognized in other comprehensive (income) loss	(22.4)	20.2	2.0
Total recognized in net periodic benefit cost and other comprehensive (income) loss	$ (14.8)	$ 27.3	$ 8.5