Quarterly Financial Data - Unaudited - Schedule of Quarterly Financial Data - Unaudited (Detail) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 24, 2016 USD ($) JointVenture $ / shares shares	Jun. 25, 2016 USD ($) $ / shares shares	Mar. 26, 2016 USD ($) $ / shares shares	Dec. 26, 2015 USD ($) $ / shares shares	Sep. 26, 2015 USD ($) $ / shares shares	Jun. 27, 2015 USD ($) $ / shares shares	Mar. 28, 2015 USD ($) $ / shares shares	Dec. 27, 2014 USD ($) $ / shares shares	Sep. 24, 2016 USD ($) JointVenture $ / shares shares	Sep. 26, 2015 USD ($) $ / shares shares	Sep. 27, 2014 USD ($) $ / shares shares
Quarterly Financial Information Disclosure [Abstract]
Net sales	$ 413,412	$ 514,544	$ 541,249	$ 359,812	$ 386,369	$ 459,446	$ 497,602	$ 307,320	$ 1,829,017	$ 1,650,737	$ 1,604,357
Gross profit	120,180	163,745	169,339	99,786	107,972	142,037	150,062	87,981	553,050	488,052	454,024
Net income (loss) attributable to Central Garden & Pet Company	$ (5,611)	$ 26,030	$ 32,697	$ (8,602)	$ (4,369)	$ 18,800	$ 23,237	$ (5,697)	$ 44,514	$ 31,971	$ 8,804
Net income per share attributable to Central Garden & Pet Company:
Basic (in usd per share) | $ / shares	$ (0.11)	$ 0.53	$ 0.67	$ (0.18)	$ (0.09)	$ 0.39	$ 0.48	$ (0.12)	$ 0.91	$ 0.66	$ 0.18
Diluted (in usd per share) | $ / shares	$ (0.11)	$ 0.51	$ 0.65	$ (0.18)	$ (0.09)	$ 0.38	$ 0.47	$ (0.12)	$ 0.87	$ 0.64	$ 0.18
Weighted average common shares outstanding:
Basic (in shares) | shares	49,453	49,120	48,717	48,566	48,322	48,167	48,384	49,379	48,964	48,562	48,880
Diluted (in shares) | shares	49,453	51,063	50,445	48,566	48,322	49,290	49,439	49,379	51,075	49,638	49,397
Debt instrument, redemption, incremental expense				$ 14,300
Debt instrument, redemption, incremental expense, call premium				8,300
Debt instrument, redemption, incremental expense, overlapping interest expenses				$ 2,700
Debt instrument, redemption, incremental expense, overlapping interest expenses, period				30 days
Write-off of deferred financing costs				$ 3,300					$ 3,337	$ 537	$ 1,731
Gain on sale of manufacturing plant assets		$ 2,400
Non-cash impairment charge	$ 16,600								$ 19,367	7,272	$ 5,870
Number of joint ventures | JointVenture	2								2
Non-cash impairment charge to indefinite-lived intangible assets	$ 1,800				$ 7,300				$ 1,800	$ 7,300