Significant Accounting Policies and Practices - Error Corrections Impact on Balance Sheet (Details) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Deferred charges and other	$ 48.3	$ 67.2
Total assets	5,107.3	5,246.0
Other current liabilities	205.6	214.2
Current liabilities	944.9	1,140.1
Deferred income taxes	65.4	50.6
Total liabilities	3,691.5	3,517.1
Accumulated earnings	243.9	223.8
Total shareholders' equity	1,407.5	1,720.9
Total equity	1,415.8	1,728.9	$ 1,589.6	$ 1,946.9
Total liabilities and equity	5,107.3	5,246.0
SB/RH
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Deferred charges and other	48.3	51.7
Total assets	5,184.3	5,291.2
Other current liabilities	195.7	182.7
Income tax payable	7.3	238.7
Current liabilities	942.3	1,354.2
Deferred income taxes	288.7	251.4
Total liabilities	3,919.1	3,856.5
Accumulated earnings	(614.2)	(414.7)
Total shareholders' equity	1,255.3	1,425.1
Total equity	1,265.2	1,434.7	$ 1,611.7	$ 1,835.4
Total liabilities and equity	$ 5,184.3	5,291.2
As reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Deferred charges and other		51.7
Total assets		5,230.5
Other current liabilities		216.0
Current liabilities		1,141.9
Deferred income taxes		55.9
Total liabilities		3,524.2
Accumulated earnings		201.2
Total shareholders' equity		1,698.3
Total equity		1,706.3
Total liabilities and equity		5,230.5
As reported | SB/RH
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Income tax payable		240.5
Current liabilities		1,356.0
Deferred income taxes		272.2
Total liabilities		3,879.1
Accumulated earnings		(437.3)
Total shareholders' equity		1,402.5
Total equity		1,412.1
Adjustment | Return-To-Provision Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Deferred charges and other		15.5
Total assets		15.5
Other current liabilities		(1.8)
Current liabilities		(1.8)
Deferred income taxes		(5.3)
Total liabilities		(7.1)
Accumulated earnings		22.6
Total shareholders' equity		22.6
Total equity		22.6
Total liabilities and equity		15.5
Adjustment | SB/RH | Return-To-Provision Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Income tax payable		(1.8)
Current liabilities		(1.8)
Deferred income taxes		(20.8)
Total liabilities		(22.6)
Accumulated earnings		22.6
Total shareholders' equity		22.6
Total equity		$ 22.6