Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Total Jacobs Stockholders' Equity	Non- controlling Interests
Balances at Sep. 26, 2014	$ 4,505,660	$ 131,753	$ 1,173,858	$ 3,527,193	$ (363,549)	$ 4,469,255	$ 36,405
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	328,882			302,971		302,971	25,911
Foreign currency translation adjustments	(136,168)				(136,168)	(136,168)
Pension liability, net of deferred taxes	32,770				32,770	32,770
Gain\(Loss) on derivatives, net of deferred taxes	2,183				2,183	2,183
Noncontrolling interest acquired / consolidated	(82)		0	(9,709)		(9,709)	9,627
Distributions to noncontrolling interests	(7,230)			0		0	(7,230)
Issuances of equity securities, net of deferred taxes	82,391	1,590	80,801			82,391
Repurchases of equity securities	(451,948)	(10,190)	(117,515)	(324,243)		(451,948)
Balances at Oct. 02, 2015	4,356,458	123,153	1,137,144	3,496,212	(464,764)	4,291,745	64,713
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	214,515			210,463		210,463	4,052
Foreign currency translation adjustments	(46,516)				(46,516)	(46,516)
Pension liability, net of deferred taxes	(98,185)				(98,185)	(98,185)
Gain\(Loss) on derivatives, net of deferred taxes	(1,129)				(1,129)	(1,129)
Noncontrolling interest acquired / consolidated	(1,277)		(127)			(127)	(1,150)
Distributions to noncontrolling interests	(5,855)			(3,146)		(3,146)	(2,709)
Issuances of equity securities, net of deferred taxes	73,406	1,351	72,055			73,406
Repurchases of equity securities	(161,235)	(3,553)	(40,800)	(116,882)		(161,235)
Balances at Sep. 30, 2016	4,330,182	120,951	1,168,272	3,586,647	(610,594)	4,265,276	64,906
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	287,375			293,727		293,727	(6,352)
Foreign currency translation adjustments	(140,527)				(140,527)	(140,527)
Pension liability, net of deferred taxes	99,047				99,047	99,047
Gain\(Loss) on derivatives, net of deferred taxes	(1,440)				(1,440)	(1,440)
Noncontrolling interest acquired / consolidated	445						445
Dividends	(72,765)			(72,765)		(72,765)
Distributions to noncontrolling interests	(4,559)			(4,559)		(4,559)
Issuances of equity securities, net of deferred taxes	100,585	1,468	99,117			100,585
Repurchases of equity securities	(110,992)	(2,033)	(27,607)	(81,352)		(110,992)
Balances at Sep. 29, 2017	$ 4,487,351	$ 120,386	$ 1,239,782	$ 3,721,698	$ (653,514)	$ 4,428,352	$ 58,999