Reportable Segments Revenue By Sector (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 27, 2016	Mar. 29, 2015	Mar. 27, 2016	Mar. 29, 2015
Revenue by client sector
Threshold percentage for disclosure of revenue from a single client			10.00%
Revenue	$ 627,384	$ 564,763	$ 1,188,092	$ 1,145,819
International
Revenue by client sector
Revenue	206,902	173,680	342,708	320,741
U.S. commercial
Revenue by client sector
Revenue	174,381	157,082	362,545	330,741
U.S. federal government
Revenue by client sector
Revenue	178,015	169,324	343,037	355,034
U.S. state and local government
Revenue by client sector
Revenue	$ 68,086	$ 64,677	$ 139,802	$ 139,303