Reportable Segments - Revenue By Client Sector (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jul. 01, 2018	Jul. 02, 2017	Jul. 01, 2018	Jul. 02, 2017
Revenue by client sector
Revenue	$ 764,795	$ 685,539	$ 2,224,805	$ 2,018,171
U.S. state and local government
Revenue by client sector
Revenue	103,169	83,716	359,828	250,392
U.S. federal government
Revenue by client sector
Revenue	245,982	224,343	719,181	665,086
U.S. commercial
Revenue by client sector
Revenue	208,507	199,065	595,691	554,707
International
Revenue by client sector
Revenue	$ 207,137	$ 178,415	$ 550,105	$ 547,986