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Reportable Segments - Revenue by Sector (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Oct. 01, 2017	Jul. 02, 2017	Apr. 02, 2017	Jan. 01, 2017	Oct. 02, 2016	Jun. 26, 2016	Mar. 27, 2016	Dec. 27, 2015	Oct. 01, 2017	Oct. 02, 2016	Sep. 27, 2015
Revenue by client sector
Threshold percentage for disclosure of revenue from a single client									10.00%	10.00%	10.00%
Revenue	$ 735,188	$ 685,539	$ 663,781	$ 668,851	$ 728,508	$ 666,869	$ 627,384	$ 560,708	$ 2,753,360	$ 2,583,469	$ 2,299,321
International
Revenue by client sector
Revenue									734,519	724,918	564,882
U.S. commercial
Revenue by client sector
Revenue									764,643	763,443	736,815
U.S. federal government
Revenue by client sector
Revenue									901,136	784,368	709,600
U.S. state and local government
Revenue by client sector
Revenue									$ 353,062	$ 310,740	$ 288,024

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- Definition

The minimum percentage of revenue from a single client that is used as a threshold for disclosure of a concentration of risk.

+ References

No definition available.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Aggregate revenue during the period from services rendered in the normal course of business, after deducting allowances and discounts.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1(d))
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

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