Goodwill and Intangible Assets - Summary of Gross Amount and Accumulated Amortization of Acquired Finite-lived Intangibles (Details) - USD ($) $ in Thousands	9 Months Ended
	Jun. 29, 2025	Sep. 29, 2024
Finite-Lived Intangible Assets [Line Items]
Gross Amount	$ 287,708	$ 314,846
Accumulated Amortization	(129,956)	(154,261)
Net Amount	$ 157,752	160,585
Client relations
Finite-Lived Intangible Assets [Line Items]
Weighted- Average Remaining Life (in Years)	7 years 7 months 6 days
Gross Amount	$ 202,749	198,726
Accumulated Amortization	(55,916)	(57,975)
Net Amount	$ 146,833	140,751
Backlog
Finite-Lived Intangible Assets [Line Items]
Weighted- Average Remaining Life (in Years)	1 year 2 months 12 days
Gross Amount	$ 46,583	75,194
Accumulated Amortization	(43,039)	(71,101)
Net Amount	$ 3,544	4,093
Trade names
Finite-Lived Intangible Assets [Line Items]
Weighted- Average Remaining Life (in Years)	8 months 12 days
Gross Amount	$ 38,376	40,926
Accumulated Amortization	(31,001)	(25,185)
Net Amount	$ 7,375	$ 15,741