Goodwill and Intangible Assets Finite Lived Assets (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 27, 2016	Mar. 29, 2015	Mar. 27, 2016	Mar. 29, 2015	Sep. 27, 2015
Finite-lived intangible assets
Gross Amount	$ 140,337		$ 140,337		$ 112,116
Accumulated Amortization	(82,104)		(82,104)		(71,784)
Foreign currency translation adjustments			1,500
Amortization expense for identifiable intangible assets	5,400	$ 4,800	9,800	$ 10,800
Estimated amortization expense
2016	12,618		12,618
2017	22,525		22,525
2018	11,863		11,863
2019	5,456		5,456
2020	4,285		4,285
Beyond	1,486		1,486
Total	58,233		$ 58,233
RME | Coffey and INDUS
Finite-lived intangible assets
Identifiable intangible assets added on acquisition	20,500
WEI | Coffey and INDUS
Finite-lived intangible assets
Identifiable intangible assets added on acquisition	5,700
Non-compete agreements
Finite-lived intangible assets
Weighted-Average Remaining Life			8 months 12 days
Gross Amount	841		$ 841		819
Accumulated Amortization	(701)		$ (701)		(587)
Client relations
Finite-lived intangible assets
Weighted-Average Remaining Life			3 years 6 months
Gross Amount	118,344		$ 118,344		106,676
Accumulated Amortization	(75,732)		$ (75,732)		(67,726)
Backlog
Finite-lived intangible assets
Weighted-Average Remaining Life			1 year 10 months 24 days
Gross Amount	18,634		$ 18,634		2,115
Accumulated Amortization	(3,429)		$ (3,429)		(1,444)
Technology and trade names
Finite-lived intangible assets
Weighted-Average Remaining Life			1 year 3 months 18 days
Gross Amount	2,518		$ 2,518		2,506
Accumulated Amortization	$ (2,242)		$ (2,242)		$ (2,027)