Reportable Segments - Revenue By Client Sector (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jul. 02, 2017	Jun. 26, 2016	Jul. 02, 2017	Jun. 26, 2016
Revenue by client sector
Revenue	$ 685,539	$ 666,869	$ 2,018,171	$ 1,854,961
U.S. federal government
Revenue by client sector
Revenue	224,343	203,663	665,086	546,700
International
Revenue by client sector
Revenue	178,415	194,616	547,986	537,324
U.S. state and local government
Revenue by client sector
Revenue	83,716	74,501	250,392	214,302
U.S. commercial
Revenue by client sector
Revenue	$ 199,065	$ 194,089	$ 554,707	$ 556,635