Goodwill and Intangible Assets - Finite Lived Assets (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Apr. 02, 2017	Mar. 27, 2016	Apr. 02, 2017	Mar. 27, 2016	Oct. 02, 2016
Finite-lived intangible assets
Gross Amount	$ 143,581		$ 143,581		$ 144,044
Accumulated Amortization	(106,268)		(106,268)		(95,082)
Amortization expense	5,900	$ 5,400	11,800	$ 9,800
Estimated amortization expense
2017	10,885		10,885
2018	14,390		14,390
2019	6,981		6,981
2020	2,759		2,759
2021	1,658		1,658
Beyond	640		640
Total	37,313		$ 37,313
Non-compete agreements
Finite-lived intangible assets
Weighted-Average Remaining Life (in Years)			6 months
Gross Amount	892		$ 892		881
Accumulated Amortization	(879)		$ (879)		(840)
Client relations
Finite-lived intangible assets
Weighted-Average Remaining Life (in Years)			2 years 10 months 24 days
Gross Amount	111,643		$ 111,643		112,367
Accumulated Amortization	(89,867)		$ (89,867)		(83,514)
Backlog
Finite-lived intangible assets
Weighted-Average Remaining Life (in Years)			1 year 8 months 12 days
Gross Amount	23,313		$ 23,313		23,018
Accumulated Amortization	(11,659)		$ (11,659)		(7,536)
Technology and trade names
Finite-lived intangible assets
Weighted-Average Remaining Life (in Years)			3 years 7 months 6 days
Gross Amount	7,733		$ 7,733		7,778
Accumulated Amortization	$ (3,863)		$ (3,863)		$ (3,192)