Other Intangible Assets - Additional Information (Detail) - USD ($)	12 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 24, 2016	Jun. 30, 2018	Dec. 24, 2016
Finite-Lived Intangible Assets [Line Items]
Indefinite-lived intangible assets, impairment charge	$ 0	$ 1,800,000	$ 1,800,000
Amortization expense for intangibles	12,700,000	$ 8,800,000	$ 5,800,000
Estimated annual amortization expense related to acquired intangible assets, 2019	12,000,000
Estimated annual amortization expense related to acquired intangible assets, 2020	12,000,000
Estimated annual amortization expense related to acquired intangible assets, 2021	12,000,000
Estimated annual amortization expense related to acquired intangible assets, 2022	12,000,000
Estimated annual amortization expense related to acquired intangible assets, 2023	$ 12,000,000
Minimum
Finite-Lived Intangible Assets [Line Items]
Weighted average remaining lives of acquired intangible assets	3 years
Maximum
Finite-Lived Intangible Assets [Line Items]
Weighted average remaining lives of acquired intangible assets	25 years
Marketing-Related Intangible Assets
Finite-Lived Intangible Assets [Line Items]
Weighted average remaining lives of acquired intangible assets	4 years
Customer-Related Intangible Assets
Finite-Lived Intangible Assets [Line Items]
Weighted average remaining lives of acquired intangible assets	10 years
Other Acquired Intangible Assets
Finite-Lived Intangible Assets [Line Items]
Weighted average remaining lives of acquired intangible assets	11 years
K&H, Bell Nursery, and General Pet Supply | Marketing-Related Intangible Assets
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, net				$ 9,600,000
K&H, Bell Nursery, and General Pet Supply | Customer-Related Intangible Assets
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, net				36,700,000
K&H, Bell Nursery, and General Pet Supply | Other Acquired Intangible Assets
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, net				$ 3,300,000
Segrest Inc. | Marketing-Related Intangible Assets
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, net					$ 2,000,000
Segrest Inc. | Customer-Related Intangible Assets
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, net					27,300,000
Segrest Inc. | Other Acquired Intangible Assets
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, net					$ 1,300,000