Balance Sheet Details - Accounts Receivable and Inventory (Details) - USD ($) $ in Millions	Dec. 30, 2018	Dec. 31, 2017
Cash and Cash Equivalents
Cash and cash equivalents	$ 182.7	$ 130.5
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total current accounts receivable	239.7	212.8
Allowance for doubtful accounts	(2.3)	(0.5)
Total accounts receivable, net	237.4	212.3
Inventory, Net of Allowances, Customer Advances and Progress Billings [Abstract]
Raw materials	34.7	35.9
Work in process	10.3	11.4
Finished goods	1.8	2.3
Subtotal inventoried costs	46.8	49.6
Less customer advances and progress payments	0.0	(0.6)
Total inventoried costs	46.8	49.0
Billed
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total current accounts receivable	66.5	74.3
Unbilled
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total current accounts receivable	173.2	138.5
U.S. Government
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total U.S. Government contract receivables	99.6	72.0
U.S. Government | Billed
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total U.S. Government contract receivables	16.5	16.9
U.S. Government | Unbilled
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total U.S. Government contract receivables	$ 83.1	$ 55.1