Accounts Receivable - Net and Revenue Recognition (Details) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Jun. 28, 2015 USD ($) claim item	Jun. 29, 2014 USD ($)	Jun. 28, 2015 USD ($) claim item	Jun. 29, 2014 USD ($)	Sep. 28, 2014 USD ($) item
Accounts Receivable - Net and Revenue Recognition
Billed	$ 317,697		$ 317,697		$ 351,693
Unbilled	318,431		318,431		363,050
Contract retentions	29,740		29,740		26,929
Total accounts receivable - gross	665,868		665,868		741,672
Allowance for doubtful accounts	(32,324)		(32,324)		(39,780)
Total accounts receivable - net	633,544		633,544		701,892
Billings in excess of costs on uncompleted contracts	92,951		$ 92,951		103,343
Period for billing and collecting unbilled receivables			12 months
Period for earning majority of billings in excess of costs			12 months
Total accounts receivable related to claims and requests for equitable adjustment on contracts	$ 53,000		$ 53,000		79,000
Number of claims settled | claim	2		2
Claims settlement amount	$ 31,000		$ 31,000
Cash proceeds from claim settlement	29,000
Revenue recognized related to the evaluation of claim amounts				$ 3,400
Reduction in the revenue related to the evaluation of claim amounts	2,000
Increase in operating income related to the evaluation of claim amounts				3,400
Decrease in operating income related to the evaluation of claim amounts	2,000
Net losses on settlement of claims			1,800
Billed accounts receivable related to U.S. federal government contracts	69,000		69,000		57,400
U.S. federal government unbilled receivables	$ 74,000		$ 74,000		$ 73,200
Threshold percentage for disclosure of accounts receivable from a single client	10.00%		10.00%		10.00%
Revenue Recognition and Contract Costs
Net favorable operating income adjustments	$ 100
Net unfavorable operating income adjustments		$ 5,000	$ 5,800	$ 10,300
Liability for anticipated losses	11,000		11,000		$ 18,600
Estimated cost to complete the related contracts	$ 69,700		$ 69,700
Accounts Receivable
Account receivable major customer
Number of clients exceeding threshold | item	0		0		0