Accumulated Other Comprehensive Income (Schedule of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 30, 2016	Dec. 29, 2017	Sep. 30, 2016
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ (85.6)	$ (72.5)	$ 0.9
Other comprehensive loss before reclassifications	(15.8)	22.7	(38.7)
Amounts reclassified from accumulated other comprehensive income	28.9	36.9	(47.8)
Ending balance	(72.5)	(12.9)	(85.6)
Currency Translation
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	1.6	(19.5)	60.2
Other comprehensive loss before reclassifications	(21.1)	16.0	0.8
Amounts reclassified from accumulated other comprehensive income	0.0	(4.7)	(59.4)
Ending balance	(19.5)	(8.2)	1.6
Unrecognized Loss on Derivatives
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(5.9)	(5.7)	(6.4)
Other comprehensive loss before reclassifications	0.0	0.0	0.0
Amounts reclassified from accumulated other comprehensive income	0.2	1.0	0.5
Ending balance	(5.7)	(4.7)	(5.9)
Unrecognized Gain (Loss) on Benefit Plans
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(81.3)	(47.3)	(52.9)
Other comprehensive loss before reclassifications	5.3	5.2	(39.5)
Amounts reclassified from accumulated other comprehensive income	28.7	40.6	11.1
Ending balance	(47.3)	(1.5)	(81.3)
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	0.0	0.0	0.0
Other comprehensive loss before reclassifications	0.0	0.0	0.0
Amounts reclassified from accumulated other comprehensive income	0.0		0.0
Ending balance	$ 0.0	$ 1.5	$ 0.0