Revenue Accounting for Contracts - Schedule of Disaggregation of Revenue / Schedules of Concentration of Risk (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 29, 2023	Sep. 30, 2022	Oct. 01, 2021
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenues	$ 16,352,414	$ 14,922,825	$ 14,092,632
U.S. Federal Government and it's Agencies | Revenue Benchmark | Customer Concentration Risk
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Concentration risk, percentage	31.00%	31.00%	33.00%
U.S. Plans
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenues	$ 10,963,072	$ 9,875,252	$ 9,671,281
Europe
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenues	3,598,140	3,488,317	3,140,114
Canada
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenues	268,466	269,386	227,692
Asia
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenues	135,359	140,663	114,118
India
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenues	164,212	114,235	70,772
Australia and New Zealand
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenues	696,870	706,283	647,866
Middle East and Africa
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenues	$ 526,295	$ 328,689	$ 220,789