Reportable Segments Revenue By Sector (Details) $ in Thousands	3 Months Ended
	Dec. 27, 2015 USD ($) item	Dec. 28, 2014 USD ($)
Revenue by client sector
Threshold percentage for disclosure of revenue from a single client	10.00%
Revenue	$ 560,708	$ 581,056
Revenue
Revenue by client sector
Number of clients exceeding threshold | item	0
International
Revenue by client sector
Revenue	$ 135,807	147,061
U.S. commercial
Revenue by client sector
Revenue	188,164	173,658
U.S. federal government
Revenue by client sector
Revenue	165,022	185,711
U.S. state and local government
Revenue by client sector
Revenue	$ 71,715	$ 74,626