Balance Sheet Details

The detail of certain assets in the consolidated balance sheets consists of the following (in millions).

Cash and cash equivalents

The Company’s cash equivalents consist of overnight cash sweep accounts that are invested on a daily basis. Cash and cash equivalents at December 31, 2017 and December 25, 2016 were $129.6 million and $69.1 million, respectively and approximated their fair value.

Accounts receivable, net (in millions)

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

Unbilled receivables represent the balance of recoverable costs and accrued profit, composed principally of revenue recognized on contracts for which billings have not been presented to the customer because the amounts were earned but not contractually billable as of the balance sheet date. Retainages receivable were $6.6 million as of December 31, 2017 and $6.2 million as of December 25, 2016 and are included in accounts receivable net.

Substantially all accounts receivable at December 31, 2017, are expected to be collected in 2018. The Company does not believe it has significant exposure to credit risk, as accounts receivable and the related unbilled amounts are primarily from contracts where the end customer is the U.S. Government.

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

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 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

Depreciation expense was $12.1 million, $12.3 million and $12.5 million for the years ended December 31, 2017, December 25, 2016, and December 27, 2015, respectively.