Consolidated Statement of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Total Jacobs Stockholders’ Equity	Total Jacobs Stockholders’ Equity Cumulative Effect, Period of Adoption, Adjustment	Noncontrolling Interests
Beginning balance at Sep. 28, 2018	$ 5,944,354	$ 142,218	$ 2,708,839	$ 3,809,991	$ (806,703)	$ 5,854,345	$ (37,209)	$ 90,009
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	723,427			705,654		705,654		17,773
Disposition of ECR business, net of deferred taxes	74,064				119,791	119,791		(45,727)
Foreign currency translation adjustments	(51,455)				(51,455)	(51,455)
Pension and retiree medical plan liability, net of deferred taxes	(25,942)				(25,942)	25,942
(Loss) Gain on derivatives, net of deferred taxes	720				720	720
Dividends	(47,407)			(47,407)		(47,407)
Noncontrolling interests - distributions and other	(14,001)					0		(14,001)
Stock based compensation	47,341		47,335	6		47,341
Noncontrolling interest acquired / consolidated	(1,113)		(1,113)			(1,113)
Issuances of equity securities including shares withheld for taxes	19,956	1,316	25,369	(6,729)		19,956
Repurchases of equity securities	(524,618)	(7,685)	(146,253)	(370,680)		(524,618)
Ending balance at Jun. 28, 2019	6,108,117	135,849	2,634,177	4,053,626	(763,589)	6,060,063		48,054
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Disposition of business, deferred taxes	5,402
Beginning balance at Mar. 29, 2019	5,555,581	136,432	2,568,809	3,620,873	(860,260)	5,465,854		89,727
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	531,064			524,442		524,442		6,622
Disposition of ECR business, net of deferred taxes	74,064				119,791	119,791		(45,727)
Foreign currency translation adjustments	(30,408)				(30,408)	(30,408)
Pension and retiree medical plan liability, net of deferred taxes	8,173				8,173	8,173
(Loss) Gain on derivatives, net of deferred taxes	(885)				(885)	(885)
Dividends	(23,477)			(23,477)		(23,477)
Noncontrolling interests - distributions and other	(2,568)							(2,568)
Stock based compensation	18,425		18,425			18,425
Noncontrolling interest acquired / consolidated	0					0
Issuances of equity securities including shares withheld for taxes	14,331	403	15,514	(1,586)		14,331
Repurchases of equity securities	(36,183)	(986)	31,429	(66,626)		(36,183)
Ending balance at Jun. 28, 2019	6,108,117	135,849	2,634,177	4,053,626	(763,589)	6,060,063		48,054
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Disposition of business, deferred taxes	5,402
Beginning balance at Sep. 27, 2019	5,768,658	132,879	2,559,450	3,939,174	(916,812)	5,714,691		53,967
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	431,517			409,855		409,855		21,662
Foreign currency translation adjustments, net of deferred taxes	8,377				8,377	8,377
Pension and retiree medical plan liability, net of deferred taxes	11,407				11,407	(11,407)
(Loss) Gain on derivatives, net of deferred taxes	(14,664)				(14,664)	(14,664)
Dividends	(50,379)			(50,379)		50,379
Noncontrolling interests - distributions and other	(21,446)		5,002			(5,002)		(26,448)
Stock based compensation	36,208		35,106	1,102		36,208
Issuances of equity securities including shares withheld for taxes	1,138	877	9,652	(9,391)		1,138
Repurchases of equity securities	(285,822)	(3,576)	(19,947)	(262,299)		285,822
Ending balance at Jun. 26, 2020	5,884,994	130,180	2,589,263	4,028,062	(911,692)	5,835,813		49,181
Beginning balance at Mar. 27, 2020	5,612,983	129,985	2,569,417	3,808,698	(946,317)	5,561,783		51,200
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	254,050			244,929		244,929		9,121
Foreign currency translation adjustments, net of deferred taxes	54,226				54,226	54,226
Pension and retiree medical plan liability, net of deferred taxes	(4,919)				(4,919)	(4,919)
(Loss) Gain on derivatives, net of deferred taxes	(14,682)				(14,682)	(14,682)
Dividends	(24,857)			(24,857)		(24,857)
Noncontrolling interests - distributions and other	(11,140)		0			0		(11,140)
Stock based compensation	12,373		12,373	0		12,373
Issuances of equity securities including shares withheld for taxes	6,960	195	7,473	(708)		6,960
Ending balance at Jun. 26, 2020	$ 5,884,994	$ 130,180	$ 2,589,263	$ 4,028,062	$ (911,692)	$ 5,835,813		$ 49,181