Balance Sheet Details

The detail of certain assets in the consolidated balance sheets consists of the following:

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 30, 2018 and December 31, 2017 were $182.7 million and $130.5 million, respectively, and approximated their fair value.

Accounts receivable, net

Receivables including amounts due under long-term contracts are summarized as follows (in millions):



	December 30, 2018			December 31, 2017
Billed, current	$	66.5		$	74.3
Unbilled, current	173.2			138.5
Total current accounts receivable	239.7			212.8
Allowance for doubtful accounts	(2.3		)	(0.5		)
Total accounts receivable, net	$	237.4		$	212.3

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.

Substantially all accounts receivable at December 30, 2018, are expected to be collected in 2019. 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 30, 2018		December 31, 2017
Billed	$	16.5	$	16.9
Unbilled	83.1		55.1
Total U.S. Government contract receivables	$	99.6	$	72.0

Inventoried costs, net of progress payments (in millions):



	December 30, 2018		December 31, 2017
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	—		(0.6		)
Total inventoried costs	$	46.8	$	49.0

Property, plant and equipment, net (in millions)



	December 30, 2018			December 31, 2017
Land and buildings	$	11.9		$	12.1
Computer equipment and software	28.3			27.3
Machinery and equipment	56.8			49.7
Furniture and office equipment	6.3			5.1
Leasehold improvements	10.9			10.1
Construction in progress	21.5			17.3
Property and equipment	135.7			121.6
Accumulated depreciation and amortization	(68.6		)	(63.6		)
Total property and equipment, net	$	67.1		$	58.0

Depreciation expense was $12.0 million, $11.8 million and $12.0 million for the years ended December 30, 2018, December 31, 2017, and December 25, 2016, respectively.