Segment Information - Financial Information Relating to Company's Business Segments (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 30, 2017	Dec. 24, 2016	Sep. 30, 2017
Net sales:
Total net sales	$ 442,011	$ 419,498
Total operating income	22,521	19,938
Interest expense - net	(7,218)	(6,835)
Other expense	(3,089)	(967)
Income tax (benefit) expense	(14,236)	4,347
Income including noncontrolling interest	26,450	7,789
Net income attributable to noncontrolling interest	203	152
Net income attributable to Central Garden & Pet Company	26,247	7,637
Depreciation and amortization:
Depreciation and amortization	11,163	10,009
Assets:
Assets	1,617,352	1,216,754	$ 1,306,906
Goodwill (included in corporate assets above):
Goodwill	256,275	230,385	256,275
Operating segments | Pet segment
Net sales:
Total net sales	325,084	304,046
Total operating income	36,176	33,406
Depreciation and amortization:
Depreciation and amortization	7,145	5,830
Assets:
Assets	620,681	575,192	612,337
Goodwill (included in corporate assets above):
Goodwill	250,802	224,912	250,802
Operating segments | Garden segment
Net sales:
Total net sales	116,927	115,452
Total operating income	2,300	2,676
Depreciation and amortization:
Depreciation and amortization	1,569	1,507
Assets:
Assets	356,821	354,674	311,026
Goodwill (included in corporate assets above):
Goodwill	5,473	5,473	5,473
Corporate
Net sales:
Total operating income	(15,955)	(16,144)
Depreciation and amortization:
Depreciation and amortization	2,449	2,672
Assets:
Assets	$ 639,850	$ 286,888	$ 383,543