Goodwill and Intangible Assets - Finite Lived Assets (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Apr. 01, 2018	Apr. 02, 2017	Apr. 01, 2018	Apr. 02, 2017	Oct. 01, 2017
Finite-lived intangible assets
Gross Amount	$ 83,158		$ 83,158		$ 118,995
Accumulated Amortization	(62,311)		(62,311)		(92,307)
Amortization expense	5,000	$ 5,900	9,700	$ 11,800
Estimated amortization expense
2018	8,300		8,300
2019	7,471		7,471
2020	2,786		2,786
2021	1,650		1,650
2022	411		411
Beyond	229		229
Total	20,847		$ 20,847
Non-compete agreements
Finite-lived intangible assets
Weighted- Average Remaining Life (in Years)			0 years
Gross Amount	83		$ 83		495
Accumulated Amortization	(83)		$ (83)		(493)
Client relations
Finite-lived intangible assets
Weighted- Average Remaining Life (in Years)			2 years 8 months 12 days
Gross Amount	54,643		$ 54,643		90,297
Accumulated Amortization	(43,119)		$ (43,119)		(75,074)
Backlog
Finite-lived intangible assets
Weighted- Average Remaining Life (in Years)			9 months 18 days
Gross Amount	23,184		$ 23,184		21,518
Accumulated Amortization	(16,443)		$ (16,443)		(13,301)
Trade names
Finite-lived intangible assets
Weighted- Average Remaining Life (in Years)			2 years 9 months 18 days
Gross Amount	5,248		$ 5,248		6,685
Accumulated Amortization	$ (2,666)		$ (2,666)		$ (3,439)