Consolidated Statements Of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Oct. 02, 2020	Sep. 27, 2019	Sep. 28, 2018
Statement of Comprehensive Income [Abstract]
Net Earnings of the Group	$ 523,867	$ 873,219	$ 173,142
Other Comprehensive Income (Loss):
Foreign currency translation adjustment	64,052	15,972	(109,877)
Gain (loss) on cash flow hedges	(21,883)	1,369
Gain (loss) on cash flow hedges			118
Change in pension and retiree medical plan liabilities	(75,334)	(157,632)	(27,231)
Other comprehensive income (loss) before taxes	(33,165)	(140,291)	(136,990)
Income Tax (Expense) Benefit:
Foreign currency translation adjustment	(3,722)	0	0
Cash flow hedges	7,285	(568)
Cash flow hedges			859
Change in pension and retiree medical plan liabilities	13,357	30,750	(17,058)
Income Tax (Expense) Benefit:	16,920	30,182	(16,199)
Net other comprehensive income (loss)	(16,245)	(110,109)	(153,189)
Net Comprehensive Income (Loss) of the Group	507,622	763,110	19,953
Net (Earnings) Loss Attributable to Noncontrolling Interests	(32,022)	(25,240)	(9,711)
Net Comprehensive Income (Loss) Attributable to Jacobs	$ 475,600	$ 737,870	$ 10,242