Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Mar. 31, 2018	Mar. 31, 2018	Mar. 31, 2017	Sep. 30, 2017
Commitment And Contingencies [Line Items]
Document Period End Date		Mar. 31, 2018
Commitments and contingencies
Inventory Recall Expense		1.6	$ 0.0
Product Liability Accrual, Period Expense	0.7	1.1
Long-term debt	5,404.2	5,404.2		5,801.9
Spectrum Brands [Member]
Commitment And Contingencies [Line Items]
Environmental costs recognized, capitalized				4.4
Product Liability Accrual, Period Expense	3.8	11.1
Spectrum Brands [Member]
Commitment And Contingencies [Line Items]
Product Liability Accrual, Component Amount	4.6	4.6		5.3
Product Warranty Accrual, Current	6.8	6.8		$ 6.4
Inventory Recall Expense		1.6
Incremental Costs To Dispose Of Product And Operational Expenses	3.1	8.4
Spectrum Brands [Member] | Spectrum Brands [Member]
Commitment And Contingencies [Line Items]
Environmental costs recognized, capitalized	$ 4.2	$ 4.2