Retirement Plans - Schedule of Net Periodic Benefit Costs (Detail) - Defined Benefit Plans - USD ($) $ in Millions	12 Months Ended
	Sep. 27, 2019	Sep. 28, 2018	Sep. 29, 2017
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 7.2	$ 7.1	$ 7.1
Interest cost	3.7	3.2	2.4
Loss due to settlement	0.9	1.0	1.4
Expected return on assets	(6.3)	(7.9)	(7.1)
Amortization of prior service cost	(0.9)	(0.7)	(0.5)
Recognized actuarial loss	2.2	2.9	4.3
Net periodic benefit cost	6.8	5.6	7.6
New prior service cost (credit)	0.8	(2.2)	(5.0)
Net (gain) loss arising during the year	32.3	(5.8)	(12.2)
Amortization of prior service cost	0.8	0.7	0.5
Amortization or settlement of net actuarial loss	(3.1)	(4.0)	(5.7)
Total recognized in other comprehensive (earnings) loss	30.8	(11.3)	(22.4)
Total recognized in net periodic benefit cost and other comprehensive (earnings) loss	$ 37.6	$ (5.7)	$ (14.8)