Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Total Jacobs Stockholders’ Equity	Total Jacobs Stockholders’ Equity Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Additional Paid-in Capital	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interests
Balance at the beginning of the period at Sep. 29, 2017	$ 4,487,351		$ 4,428,352		$ 120,386	$ 1,239,782	$ 3,721,698		$ (653,514)	$ 58,999
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	173,142		163,431				163,431			9,711
Foreign currency translation adjustments	(109,877)		(109,877)						(109,877)
Pension liability, net of deferred taxes	(34,129)		(34,129)				10,160		(44,289)
(Loss) gain on derivatives, net of deferred taxes	977		977						977
Noncontrolling interest acquired/consolidated	37,146		3,456			3,456				33,690
Dividends	(85,608)		(85,608)				(85,608)
Noncontrolling interests - distributions and other	(4,686)		7,705				7,705			(12,391)
Stock based compensation	79,242		79,242			81,196	(1,954)
Issuances of equity securities, net of deferred taxes	1,403,777		1,403,777		21,881	1,385,316	(3,420)
Other	(2,981)		(2,981)		(49)	(911)	(2,021)
Balance at the end of the period at Sep. 28, 2018	5,944,354	$ (37,209)	5,854,345	$ (37,209)	142,218	2,708,839	3,809,991	$ (37,209)	(806,703)	90,009
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	873,219		847,979				847,979			25,240
Disposition of ECR business, net of deferred taxes	67,037		112,764						112,764	(45,727)
Foreign currency translation adjustments	(84,456)		(84,456)						(84,456)
Pension liability, net of deferred taxes	(139,218)		(139,218)						(139,218)
(Loss) gain on derivatives, net of deferred taxes	801		801						801
Noncontrolling interest acquired/consolidated	(1,113)		(1,113)			(1,113)
Dividends	(92,980)		(92,980)				(92,980)
Noncontrolling interests - distributions and other	(15,555)									(15,555)
Stock based compensation	69,137		69,137			69,128	9
Issuances of equity securities, net of deferred taxes	38,317		38,317		1,681	43,508	(6,872)
Other	(853,676)		(853,676)		(11,020)	(260,912)	(581,744)
Balance at the end of the period at Sep. 27, 2019	5,768,658		5,714,691		132,879	2,559,450	3,939,174		(916,812)	53,967
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	523,867		491,845				491,845			32,022
Foreign currency translation adjustments	60,330		60,330						60,330
Pension liability, net of deferred taxes	(61,977)		(61,977)						(61,977)
(Loss) gain on derivatives, net of deferred taxes	(14,598)		(14,598)						(14,598)
Dividends	(99,921)		(99,921)				(99,921)
Noncontrolling interests - distributions and other	(41,032)		5,002			5,002				(46,034)
Stock based compensation	48,150		48,150			47,048	1,102
Issuances of equity securities, net of deferred taxes	9,441		9,441		998	17,890	(9,447)
Other	(337,251)		(337,251)		(4,129)	(30,944)	(302,178)
Balance at the end of the period at Oct. 02, 2020	$ 5,855,667		$ 5,815,712		$ 129,748	$ 2,598,446	$ 4,020,575		$ (933,057)	$ 39,955