Segment Information - Financial Information Relating to Company's Business Segments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 27, 2021	Mar. 28, 2020	Mar. 27, 2021	Mar. 28, 2020	Sep. 26, 2020
Net sales:
Net sales	$ 935,252	$ 703,229	$ 1,527,482	$ 1,186,057
Operating Income
Total operating income	104,610	66,105	131,650	68,170
Interest expense - net	(10,151)	(9,336)	(30,920)	(17,973)
Other income (expense)	704	(979)	1,456	(674)
Income tax expense	21,564	12,648	22,945	10,920
Income including noncontrolling interest	73,599	43,142	79,241	38,603
Net income attributable to noncontrolling interest	645	438	674	316
Net income attributable to Central Garden & Pet Company	72,954	42,704	78,567	38,287
Depreciation and amortization:
Depreciation and amortization	18,854	13,176	31,769	26,316
Assets:
Assets	2,847,102	2,167,407	2,847,102	2,167,407	$ 2,339,364
Goodwill (included in corporate assets above):
Goodwill	289,955	289,854	289,955	289,854	289,955
Pet Segment
Net sales:
Net sales	491,972	405,528	928,382	772,119
Garden Segment
Net sales:
Net sales	443,280	297,701	599,100	413,938
Operating segments | Pet Segment
Operating Income
Total operating income	62,058	43,476	105,583	72,213
Depreciation and amortization:
Depreciation and amortization	8,882	9,170	17,967	18,242
Assets:
Assets	980,769	894,294	980,769	894,294	877,901
Goodwill (included in corporate assets above):
Goodwill	277,067	276,966	277,067	276,966	277,067
Operating segments | Garden Segment
Operating Income
Total operating income	65,962	43,161	70,613	36,278
Depreciation and amortization:
Depreciation and amortization	8,804	2,595	11,442	5,308
Assets:
Assets	1,511,136	613,847	1,511,136	613,847	481,401
Goodwill (included in corporate assets above):
Goodwill	12,888	12,888	12,888	12,888	12,888
Corporate
Operating Income
Total operating income	(23,410)	(20,532)	(44,546)	(40,321)
Depreciation and amortization:
Depreciation and amortization	1,168	1,411	2,360	2,766
Assets:
Assets	$ 355,197	$ 659,266	$ 355,197	$ 659,266	$ 980,062