Retirement Plans (Schedule of Benefit Obligation, Plan Assets and Funded Status of Plans) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 30, 2016	Dec. 29, 2017	Dec. 30, 2016	Sep. 30, 2016	Sep. 25, 2015
Pension Benefits
Change in benefit obligations:
Projected benefit obligations at beginning of year	$ 409.1	$ 257.4		$ 375.5
Service cost	0.8	1.4		1.8	$ 2.4
Interest cost	2.0	2.3		13.2	14.5
Actuarial (gain) loss	(23.2)	(9.0)		65.5
Defined Benefit Plan, Benefit Obligation, Benefits Paid	(5.3)	(9.4)		(20.1)
Plan settlements	(125.9)	(217.0)		(26.5)
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment	0.0	0.0		(0.4)
Net transfer in	1.1	0.0		0.0
Currency translation	(1.2)	2.1		0.1
Projected benefit obligations at end of year	257.4	27.8	$ 257.4	409.1	375.5
Change in plan assets:
Fair value of plan assets at beginning of year	309.5	161.0		309.9
Actual return on plan assets	(18.1)	0.3		29.5
Employer contributions	0.8	68.0		16.7
Defined Benefit Plan, Plan Assets, Benefits Paid	(5.3)	(9.4)		(20.1)
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Assets Transferred to (from) Plan	0.0	(2.9)		0.0
Plan settlements	(125.9)	(217.0)		(26.5)
Fair value of plan assets at end of year	161.0	0.0	161.0	309.5	309.9
Funded status at end of year	(96.4)	(27.8)	(96.4)	(99.6)
Postretirement Benefits
Change in benefit obligations:
Projected benefit obligations at beginning of year	50.8	47.5		52.2
Service cost	0.1	0.0		0.1	0.1
Interest cost	0.4	1.7		2.0	1.9
Actuarial (gain) loss	(2.8)	0.2		0.5
Defined Benefit Plan, Benefit Obligation, Benefits Paid	(1.0)	(2.9)		(4.0)
Plan settlements	0.0	(0.9)		0.0
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment	0.0	0.0		0.0
Net transfer in	0.0	0.0		0.0
Currency translation	0.0	0.0		0.0
Projected benefit obligations at end of year	47.5	45.6	47.5	50.8	52.2
Change in plan assets:
Fair value of plan assets at beginning of year	0.0	0.0	0.0	0.0
Actual return on plan assets		0.0	0.0	0.0
Employer contributions		2.9	1.0	4.0
Defined Benefit Plan, Plan Assets, Benefits Paid		(2.9)	(1.0)	(4.0)
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Assets Transferred to (from) Plan				0.0
Plan settlements		0.0	0.0	0.0
Fair value of plan assets at end of year	0.0	0.0	0.0	0.0	$ 0.0
Funded status at end of year	$ (47.5)	$ (45.6)	$ (47.5)	$ (50.8)