Consolidated Statements Of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended
	Dec. 29, 2017	Dec. 30, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net Earnings of the Group	$ 2,561	$ 61,153
Other Comprehensive Income (Loss):
Foreign currency translation adjustment	20,168	(287,524)
Gain (loss) on cash flow hedges	890	(942)
Change in pension liabilities	3,596	24,753
Other comprehensive income (loss) before taxes	24,654	(263,713)
Income Tax Expense:
Cash flow hedges		(82)
Change in pension liabilities	(125)	(4,522)
Income Tax Expense:	(125)	(4,604)
Net other comprehensive income (loss)	24,529	(268,317)
Net Comprehensive Income (Loss) of the Group	27,090	(207,164)
Net Earnings Attributable to Noncontrolling Interests	(398)	(617)
Net Comprehensive Income (Loss) Attributable to Jacobs	$ 26,692	$ (207,781)