Related Party Transactions (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 28, 2025	Jun. 29, 2025	Mar. 30, 2025	Dec. 29, 2024	Sep. 29, 2024	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023	Sep. 28, 2025	Sep. 29, 2024	Oct. 01, 2023
Related Party Transaction [Line Items]
Revenue	$ 1,330,100	$ 1,369,816	$ 1,322,113	$ 1,420,561	$ 1,374,473	$ 1,344,323	$ 1,251,616	$ 1,228,267	$ 5,442,590	$ 5,198,679	$ 4,522,550
Related reimbursable costs									57,777	61,637	78,489
Accounts receivable, net	1,158,928				1,051,461				1,158,928	1,051,461
Contract assets	138,232				129,678				138,232	129,678
Contract liabilities	(420,254)				(351,738)				(420,254)	(351,738)
Related Party
Related Party Transaction [Line Items]
Revenue									64,454	67,744	$ 83,148
Accounts receivable, net	14,848				15,612				14,848	15,612
Contract assets	1,154				1,625				1,154	1,625
Contract liabilities	$ (6,583)				$ (4,237)				$ (6,583)	$ (4,237)