Revenues - Schedule of Disaggregation of Revenue (Details) - USD ($) $ in Millions	12 Months Ended
	Oct. 03, 2025	Sep. 27, 2024	Sep. 29, 2023
Disaggregation of Revenue [Line Items]
Total revenues	$ 14,393	$ 8,388	$ 7,865
DS
Disaggregation of Revenue [Line Items]
Total revenues	5,543	1,981	1,899
GES
Disaggregation of Revenue [Line Items]
Total revenues	8,850	6,407	5,966
Department of War and U.S. Intelligence Community
Disaggregation of Revenue [Line Items]
Total revenues	7,678	5,603	5,265
Department of War and U.S. Intelligence Community | DS
Disaggregation of Revenue [Line Items]
Total revenues	3,222	1,509	1,474
Department of War and U.S. Intelligence Community | GES
Disaggregation of Revenue [Line Items]
Total revenues	4,456	4,094	3,791
Other U.S. Government Agencies
Disaggregation of Revenue [Line Items]
Total revenues	3,994	1,984	1,867
Other U.S. Government Agencies | DS
Disaggregation of Revenue [Line Items]
Total revenues	1,607	386	341
Other U.S. Government Agencies | GES
Disaggregation of Revenue [Line Items]
Total revenues	2,387	1,598	1,526
Commercial and International
Disaggregation of Revenue [Line Items]
Total revenues	2,721	801	733
Commercial and International | DS
Disaggregation of Revenue [Line Items]
Total revenues	714	86	84
Commercial and International | GES
Disaggregation of Revenue [Line Items]
Total revenues	2,007	715	649
United States
Disaggregation of Revenue [Line Items]
Total revenues	10,746	6,055	5,748
United States | DS
Disaggregation of Revenue [Line Items]
Total revenues	5,304	1,679	1,544
United States | GES
Disaggregation of Revenue [Line Items]
Total revenues	5,442	4,376	4,204
International
Disaggregation of Revenue [Line Items]
Total revenues	3,647	2,333	2,117
International | DS
Disaggregation of Revenue [Line Items]
Total revenues	239	302	355
International | GES
Disaggregation of Revenue [Line Items]
Total revenues	3,408	2,031	1,762
Prime contractor
Disaggregation of Revenue [Line Items]
Total revenues	13,096	7,510	6,958
Prime contractor | DS
Disaggregation of Revenue [Line Items]
Total revenues	5,069	1,772	1,722
Prime contractor | GES
Disaggregation of Revenue [Line Items]
Total revenues	8,027	5,738	5,236
Subcontractor
Disaggregation of Revenue [Line Items]
Total revenues	1,297	878	907
Subcontractor | DS
Disaggregation of Revenue [Line Items]
Total revenues	474	209	177
Subcontractor | GES
Disaggregation of Revenue [Line Items]
Total revenues	823	669	730
Cost-plus-fee
Disaggregation of Revenue [Line Items]
Total revenues	8,983	5,198	4,941
Cost-plus-fee | DS
Disaggregation of Revenue [Line Items]
Total revenues	3,557	964	875
Cost-plus-fee | GES
Disaggregation of Revenue [Line Items]
Total revenues	5,426	4,234	4,066
Fixed-price
Disaggregation of Revenue [Line Items]
Total revenues	3,489	2,226	2,089
Fixed-price | DS
Disaggregation of Revenue [Line Items]
Total revenues	1,422	650	667
Fixed-price | GES
Disaggregation of Revenue [Line Items]
Total revenues	2,067	1,576	1,422
Time-and-materials
Disaggregation of Revenue [Line Items]
Total revenues	1,921	964	835
Time-and-materials | DS
Disaggregation of Revenue [Line Items]
Total revenues	564	367	357
Time-and-materials | GES
Disaggregation of Revenue [Line Items]
Total revenues	$ 1,357	$ 597	$ 478