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Savings and Deferred Compensation Plans Savings and Deferred Compensation Plans (Savings Plans) (Details) - USD ($) $ in Thousands	12 Months Ended
	Oct. 01, 2021	Oct. 02, 2020	Sep. 27, 2019
Savings And Deferred Compensation Plans [Abstract]
Savings plans contributions	$ 132,865	$ 91,833	$ 114,006

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- Definition

Defined Contribution Plan Savings Plans Contributions

+ References

No definition available.

+ Details

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- Definition

Savings And Deferred Compensation Plans [Abstract]

+ References

No definition available.

+ Details

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Namespace Prefix:	jec_
Data Type:	xbrli:stringItemType
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