Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Dec. 30, 2018	Dec. 31, 2017	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Effective tax rate (as a percent)	20.40%	(1.40%)
Statutory federal tax rate			24.50%
Deferred tax benefit from tax reform remeasurement	$ 2.6	$ 10.1
Effective income tax rate excluding revaluation of deferred taxes (as a percent)	25.30%	20.90%
Deferred tax liability valuation allowance	$ 14.4
Liability for uncertain tax positions	$ 11.6		$ 9.4
Period during which unrecognized tax benefits would affect the effective tax rate	12 months