Accounts Receivable - Net (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 27, 2015 USD ($) item	Dec. 28, 2014 USD ($)	Sep. 27, 2015 USD ($) item
Accounts Receivable, Net
Billed	$ 335,873		$ 331,364
Unbilled	271,578		311,823
Contract retentions	24,221		24,333
Total accounts receivable - gross	631,672		667,520
Allowance for doubtful accounts	(37,704)		(31,490)
Total accounts receivable - net	593,968		636,030
Billings in excess of costs on uncompleted contracts	$ 96,188		93,989
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	$ 39,000		53,000
Revenue recognized related to the evaluation of claim amounts		$ 3,200
Increase in operating income related to the evaluation of claim amounts		3,200
Billed accounts receivable related to U.S. federal government contracts	58,000		61,900
U.S. federal government unbilled receivables	$ 62,300		$ 74,200
Threshold percentage for disclosure of accounts receivable from a single client	10.00%		10.00%
Revenue Recognition and Contract Costs
Net unfavorable operating income adjustments		$ 2,400
Liability for anticipated losses	$ 8,600		$ 10,500
Estimated cost to complete the related contracts	$ 47,700
Accounts Receivable
Account receivable major customer
Number of clients exceeding threshold | item	0		0
RCM
Accounts Receivable, Net
Cash proceeds from claim settlement	$ 13,400
Claims amount	8,800
Gain from claim settlement	4,600
Increase in allowance for doubtful accounts	7,900
Decrease in operating income related to the increase in allowance for doubtful accounts	7,900
Collectability of certain accounts receivable	$ 4,600