Restructuring and related charges - Summarization of Restructuring and Related Charges (Detail) - USD ($) $ in Millions	3 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 20.4	$ 2.2
Consumer products cost of goods sold classification
Restructuring Cost and Reserve [Line Items]
Restructuring charges	1.8	1.1
Selling, acquisition, operating and general expenses classification
Restructuring Cost and Reserve [Line Items]
Restructuring charges	18.6	1.1
Global Cost Reduction Initiatives
Restructuring Cost and Reserve [Line Items]
Restructuring charges	4.0	1.5
Global Expense Rationalization Initiatives
Restructuring Cost and Reserve [Line Items]
Total Projected Costs	35.0
HHI Distribution Center Consolidation [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges	15.2	0.0
Total Projected Costs	55.0
Pet Rightsizing Initiative [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0.6	0.0
Total Projected Costs	9.0
Other initiatives
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 0.6	$ 0.7

Amount expected to be recognized in earnings for the specified restructuring cost.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 5.P.4(b))
-URI http://asc.fasb.org/extlink&oid=27011515&loc=d3e140904-122747

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Discloses the amount charged against the accrued restructuring reserves, or earnings if not previously accrued, during the period for the specified type of restructuring cost.

+ References

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