Balance Sheet Details (Tables)

12 Months Ended

Dec. 31, 2017

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Schedule of Accounts, Notes, Loans and Financing Receivable

U.S. Government contract receivables where the Company is the prime contractor included in accounts receivable, net (in millions)

	December 31, 2017		December 25, 2016
Billed	$	17.3	$	15.6
Unbilled	55.3		39.3
Total U.S. Government contract receivables	$	72.6	$	54.9

Receivables including amounts due under long-term contracts are summarized as follows:

	December 31, 2017			December 25, 2016
Billed, current	$	101.5		$	102.8
Unbilled, current	167.5			128.3
Total current accounts receivable	269.0			231.1
Allowance for doubtful accounts	(0.6		)	(1.7		)
Total accounts receivable, net	$	268.4		$	229.4

Schedule of Inventory, Current

Inventoried costs, net of progress payments (in millions)

	December 31, 2017			December 25, 2016
Raw materials	$	35.4		$	31.9
Work in process	11.4			22.1
Finished goods	2.3			1.4
Supplies and other	1.9			1.8
Subtotal inventoried costs	51.0			57.2
Less customer advances and progress payments	(0.6		)	(1.8		)
Total inventoried costs	$	50.4		$	55.4

Property, Plant and Equipment

Assets are depreciated predominately using the straight-line method, with the following lives:

	Years
Buildings and improvements	15 – 39
Machinery and equipment	3 – 10
Computer equipment and software	1 – 10
Vehicles, furniture, and office equipment	5
Leasehold improvements	Shorter of useful life or length of lease

Property and equipment, net (in millions)

	December 31, 2017			December 25, 2016
Land and buildings	$	12.1		$	12.2
Computer equipment and software	30.1			26.9
Machinery and equipment	49.9			47.2
Furniture and office equipment	5.7			5.3
Leasehold improvements	11.2			9.9
Construction in progress	19.8			6.1
Property and equipment	128.8			107.6
Accumulated depreciation and amortization	(67.6		)	(57.8		)
Total property and equipment, net	$	61.2		$	49.8