Business Segment Data - Class of Similar Products Which Represented Approximately 10% or More of Company's Consolidated Net Sales (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 26, 2020	Jun. 27, 2020	Mar. 28, 2020	Dec. 28, 2019	Sep. 28, 2019	Jun. 29, 2019	Mar. 30, 2019	Dec. 29, 2018	Sep. 26, 2020	Sep. 28, 2019	Sep. 29, 2018
Revenue from External Customer [Line Items]
Revenues	$ 675,969	$ 833,483	$ 703,229	$ 482,828	$ 540,744	$ 706,575	$ 673,701	$ 461,990	$ 2,695,509	$ 2,383,010	$ 2,215,362
Other pet products
Revenue from External Customer [Line Items]
Revenues									705,200	613,400	606,700
Other garden products
Revenue from External Customer [Line Items]
Revenues									607,600	560,800	445,700
Other manufacturers' products
Revenue from External Customer [Line Items]
Revenues									600,700	504,500	454,300
Dog & cat products
Revenue from External Customer [Line Items]
Revenues									502,100	452,100	445,100
Controls & fertilizer products
Revenue from External Customer [Line Items]
Revenues									$ 279,900	$ 252,200	$ 263,600