Retirement Plans (Defined Contribution Plan) (Details) - Defined Contribution Plan, 401 K [Member] - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 30, 2016	Dec. 29, 2017	Sep. 30, 2016	Sep. 25, 2015
Defined Contribution Plan Disclosure [Line Items]
Employer matching contribution, percent of match		50.00%
Defined Contribution Plan, Cost	$ 4.2	$ 25.2	$ 25.3	$ 22.1