Income Taxes - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Mar. 31, 2019	Apr. 01, 2018	Mar. 31, 2019	Apr. 01, 2018	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Effective tax rate (as a percent)			(0.80%)	11.00%
Statutory federal tax rate					24.50%
Deferred tax benefit from tax reform remeasurement	$ 2.6	$ 10.1
Deferred tax liability valuation allowance	$ 22.3		$ 22.3
Effective income tax rate excluding revaluation of deferred taxes (as a percent)	24.80%	23.00%
Liability for uncertain tax positions	$ 12.1		$ 12.1		$ 9.4
Period during which unrecognized tax benefits would affect the effective tax rate			12 months