Acquisitions - Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 25, 2022	May 23, 2022	Dec. 27, 2021
Business Acquisition [Line Items]
Goodwill	$ 569.1	$ 558.2
Cosmic Advanced Engineering Solutions, Inc.
Business Acquisition [Line Items]
Accounts receivable				$ 3.8
Unbilled receivables				4.1
Other current assets				0.1
Property and equipment				1.3
Intangible assets				8.5
Total identifiable net assets acquired				17.8
Total identifiable net liabilities assumed				(9.1)
Goodwill				29.2
Net assets acquired, excluding cash				$ 37.9
Southern Research Engineering Division
Business Acquisition [Line Items]
Accounts receivable			$ 2.9
Unbilled receivables			11.1
Inventory			0.5
Other current assets			0.2
Property and equipment			22.8
Other assets			0.2
Intangible assets			10.8
Total identifiable net assets acquired			48.5
Total identifiable net liabilities assumed			(3.4)
Goodwill			34.3
Net assets acquired, excluding cash			$ 79.4