Goodwill and intangible assets - Schedule of Goodwill (Details) $ in Millions	3 Months Ended
	Dec. 31, 2019 USD ($)
Goodwill [Roll Forward]
Beginning balance	$ 1,004.8
Cumulative translation adjustment	12.9
Ending balance	1,022.5
Americas
Goodwill [Roll Forward]
Beginning balance	861.6
Cumulative translation adjustment	0.3
Ending balance	866.4
International
Goodwill [Roll Forward]
Beginning balance	143.2
Cumulative translation adjustment	12.6
Ending balance	156.1
Spectrum Brands Holdings
Goodwill [Roll Forward]
Goodwill acquired	0.9
Spectrum Brands Holdings | Americas
Goodwill [Roll Forward]
Goodwill acquired	0.7
Spectrum Brands Holdings | International
Goodwill [Roll Forward]
Goodwill acquired	0.2
Spectrum Auto Care Acquisition
Goodwill [Roll Forward]
Goodwill acquired	3.9
Spectrum Auto Care Acquisition | Americas
Goodwill [Roll Forward]
Goodwill acquired	3.8
Spectrum Auto Care Acquisition | International
Goodwill [Roll Forward]
Goodwill acquired	$ 0.1