Accounts Receivable - Net (Details) (USD $)	12 Months Ended
	Sep. 28, 2014 item	Sep. 29, 2013 item	Sep. 30, 2012 item
Billed	$ 351,693,000	$ 375,149,000
Unbilled	363,050,000	306,969,000
Contract retentions	26,929,000	23,353,000
Total accounts receivable - gross	741,672,000	705,471,000
Allowance for doubtful accounts	(39,780,000)	(44,624,000)
Total accounts receivable - net	701,892,000	660,847,000
Billings in excess of costs on uncompleted contracts	103,343,000	79,507,000
Period for billing and collecting unbilled receivables	12 months
Period for earning majority of billings in excess of costs	12 months
Unbilled accounts receivable related to claims and requests for equitable adjustment on contracts	79,000,000	41,000,000
Revenue recognized related to the evaluation of claim amounts	3,400,000
Increase in operating income related to the evaluation of claim amounts	3,400,000
Billed accounts receivable related to U.S. federal government contracts	57,400,000	50,500,000
U.S. federal government unbilled receivables	73,200,000	79,300,000
Threshold percentage for disclosure of accounts receivable from a single client	10.00%	10.00%
Loss on uncollectible accounts receivable related to claims		$ 30,200,000
Accounts Receivable
Number of clients exceeding threshold	0	0	0