Balance Sheet Details - Accounts Receivable and Inventory (Details) (USD $) In Millions, unless otherwise specified	Dec. 29, 2013	Dec. 30, 2012	Dec. 25, 2011	Dec. 26, 2010
Cash and Cash Equivalents [Abstract]
Cash and cash equivalents	$ 55.7	$ 49.0	$ 69.6	$ 10.8
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total current accounts receivable	268.1	273.3
Allowance for doubtful accounts	(2.3)	(1.4)
Total current accounts receivable, net	265.8	271.9
Total accounts receivable, net	265.9	272.2
Retainages receivable	6.2	3.5
Inventory, Net of Allowances, Customer Advances and Progress Billings [Abstract]
Raw materials	44.5	48.4
Work in process	24.3	36.5
Finished goods	4.6	7.3
Supplies and other	1.9	2.2
Subtotal inventoried costs	75.3	94.4
Less customer advances and progress payments	(0.7)	(0.1)
Total inventoried costs	74.6	94.3
Billed
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total current accounts receivable	150.2	137.9
Unbilled
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total current accounts receivable	117.9	135.4
Unbilled, long-term (included in other assets)	0.1	0.3
U.S. Government
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable, net	51.4	64.0
U.S. Government | Billed
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable, net	19.8	24.6
U.S. Government | Unbilled
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable, net	$ 31.6	$ 39.4