Goodwill and Intangible Assets - Amortization (Details) - USD ($) $ in Thousands	12 Months Ended
	Oct. 01, 2017	Oct. 02, 2016	Sep. 27, 2015
Finite-lived intangible assets
Gross Amount	$ 118,995	$ 144,044
Accumulated Amortization	(92,307)	(95,082)
Foreign currency translation adjustments	(100)	(1,100)
Amortization expense for intangible assets	22,800	22,100	$ 20,200
Estimated amortization expense
2018	14,548
2019	7,034
2020	2,802
2021	1,664
2022	411
Beyond	229
Total	$ 26,688
Non-compete agreements
Finite-lived intangible assets
Weighted- Average Remaining Life (in years)	1 month 6 days
Gross Amount	$ 495	881
Accumulated Amortization	$ (493)	(840)
Client relations
Finite-lived intangible assets
Weighted- Average Remaining Life (in years)	2 years 10 months 24 days
Gross Amount	$ 90,297	112,367
Accumulated Amortization	$ (75,074)	(83,514)
Backlog
Finite-lived intangible assets
Weighted- Average Remaining Life (in years)	1 year 4 months 24 days
Gross Amount	$ 21,518	23,018
Accumulated Amortization	$ (13,301)	(7,536)
Technology and trade names
Finite-lived intangible assets
Weighted- Average Remaining Life (in years)	3 years 3 months 18 days
Gross Amount	$ 6,685	7,778
Accumulated Amortization	$ (3,439)	$ (3,192)