Balance Sheet Details - Accounts Receivable and Inventory (Details) - USD ($) $ in Millions	Dec. 29, 2019	Dec. 30, 2018
Cash and Cash Equivalents
Cash and cash equivalents	$ 172.6	$ 182.7
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total current accounts receivable	266.3	239.7
Allowance for doubtful accounts	(1.9)	(2.3)
Total accounts receivable and unbilled receivables, net	264.4	237.4
Inventory, Net of Allowances, Customer Advances and Progress Billings [Abstract]
Raw materials	39.1	34.7
Work in process	20.3	10.3
Finished goods	1.7	1.8
Total inventoried costs	61.1	46.8
Billed
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total current accounts receivable	86.6	66.5
Unbilled
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total current accounts receivable	179.7	173.2
U.S. Government
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total U.S. Government contract receivables	103.0	99.6
U.S. Government | Billed
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total U.S. Government contract receivables	16.6	16.5
U.S. Government | Unbilled
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total U.S. Government contract receivables	$ 86.4	$ 83.1