Revenue Accounting for Contracts - Schedule of Disaggregation of Revenue and Schedule of Concentration of Risk (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 26, 2025	Sep. 27, 2024	Sep. 29, 2023
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenues	$ 12,029,783	$ 11,500,941	$ 10,851,420
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	8.00%	10.00%	9.00%
United States
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenues	$ 7,415,464	$ 7,178,610	$ 6,511,371
Europe
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenues	2,871,566	2,689,298	2,704,684
Canada
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenues	248,118	261,682	266,926
Asia
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenues	144,944	132,658	133,670
India
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenues	180,124	152,591	164,212
Australia and New Zealand
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenues	573,237	549,571	558,096
Middle East and Africa
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenues	$ 596,330	$ 536,531	$ 512,461