Balance Sheet Details - Accounts Receivable and Unbilled Receivables (Details) - USD ($) $ in Millions	Dec. 27, 2020	Dec. 29, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total current accounts receivable	$ 274.1	$ 266.3
Allowance for doubtful accounts	(1.8)	(1.9)
Total accounts receivable and unbilled receivables, net	272.3	264.4
U.S. Government
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total U.S. Government contract receivables	97.4	103.0
Billed
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total current accounts receivable	97.0	86.6
Billed | U.S. Government
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total U.S. Government contract receivables	19.5	16.6
Unbilled
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total current accounts receivable	177.1	179.7
Unbilled | U.S. Government
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total U.S. Government contract receivables	$ 77.9	$ 86.4