Goodwill and Intangible Assets - Gross Amount, Accumulated Amortization and Estimated Amortization (Details) - USD ($) $ in Thousands	12 Months Ended
Sep. 27, 2020	Sep. 29, 2019
Finite-lived intangible assets
Gross Amount	$ 106,421	$ 96,722
Accumulated Amortization	(92,478)	(80,282)
Estimated amortization expense
2021	8,786
2022	2,652
2023	1,915
2024	590
Total	$ 13,943	16,440
Client relations
Finite-lived intangible assets
Weighted- Average Remaining Life (in years)	2 years 10 months 24 days
Gross Amount	$ 60,775	56,779
Accumulated Amortization	$ (53,392)	(50,455)
Backlog
Finite-lived intangible assets
Weighted- Average Remaining Life (in years)	8 months 12 days
Gross Amount	$ 37,682	32,229
Accumulated Amortization	$ (32,761)	(24,968)
Technology and trade names
Finite-lived intangible assets
Weighted- Average Remaining Life (in years)	1 year 9 months 18 days
Gross Amount	$ 7,964	7,714
Accumulated Amortization	$ (6,325)	$ (4,859)

Weighted average amortization period of finite-lived intangible assets acquired either individually or as part of a group of assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16265-109275

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Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
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Amount of amortization for assets, excluding financial assets and goodwill, lacking physical substance with finite life expected to be recognized in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
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Amount of amortization for assets, excluding financial assets and goodwill, lacking physical substance with finite life expected to be recognized in fourth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of amortization for assets, excluding financial assets and goodwill, lacking physical substance with finite life expected to be recognized in third fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of amortization for assets, excluding financial assets and goodwill, lacking physical substance with finite life expected to be recognized in second fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount before amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 928
-SubTopic 340
-Section 50
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-URI http://asc.fasb.org/extlink&oid=6473545&loc=d3e61844-108004

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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.

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Amount after amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 926
-SubTopic 20
-Section 50
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-URI http://asc.fasb.org/extlink&oid=120154696&loc=d3e54445-107959

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