Segment Information - Disaggregated Revenues by Segment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 27, 2021	Mar. 28, 2020	Mar. 27, 2021	Mar. 28, 2020
Segment Reporting Information [Line Items]
Net sales	$ 935,252	$ 703,229	$ 1,527,482	$ 1,186,057
Pet Segment
Segment Reporting Information [Line Items]
Net sales	491,972	405,528	928,382	772,119
Garden Segment
Segment Reporting Information [Line Items]
Net sales	443,280	297,701	599,100	413,938
Other pet products
Segment Reporting Information [Line Items]
Net sales	259,500	208,900	441,800	359,300
Other pet products | Pet Segment
Segment Reporting Information [Line Items]
Net sales	259,500	208,900	441,800	359,300
Other pet products | Garden Segment
Segment Reporting Information [Line Items]
Net sales	0	0	0	0
Dog and cat products
Segment Reporting Information [Line Items]
Net sales	133,300	111,400	288,700	241,800
Dog and cat products | Pet Segment
Segment Reporting Information [Line Items]
Net sales	133,300	111,400	288,700	241,800
Dog and cat products | Garden Segment
Segment Reporting Information [Line Items]
Net sales	0	0	0	0
Other manufacturers' products
Segment Reporting Information [Line Items]
Net sales	188,400	150,300	329,700	266,000
Other manufacturers' products | Pet Segment
Segment Reporting Information [Line Items]
Net sales	99,200	85,200	197,900	171,000
Other manufacturers' products | Garden Segment
Segment Reporting Information [Line Items]
Net sales	89,200	65,100	131,800	95,000
Garden controls and fertilizer products
Segment Reporting Information [Line Items]
Net sales	131,700	110,800	160,800	133,900
Garden controls and fertilizer products | Pet Segment
Segment Reporting Information [Line Items]
Net sales	0	0	0	0
Garden controls and fertilizer products | Garden Segment
Segment Reporting Information [Line Items]
Net sales	131,700	110,800	160,800	133,900
Other garden supplies
Segment Reporting Information [Line Items]
Net sales	222,400	121,800	306,500	185,100
Other garden supplies | Pet Segment
Segment Reporting Information [Line Items]
Net sales	0	0	0	0
Other garden supplies | Garden Segment
Segment Reporting Information [Line Items]
Net sales	$ 222,400	$ 121,800	$ 306,500	$ 185,000