Certain Balance Sheet Components



Accounts receivable, net	September 30, 2014		December 31, 2013
	(in thousands)
Trade receivables (net of allowance of $6,524 and $8,368)	$	310,261	$	328,240
Unbilled receivables	32,219		28,469
Total accounts receivable, net	$	342,480	$	356,709

At September 30, 2014 and December 31, 2013, $4.7 million and $3.2 million, respectively, were recorded within trade receivables as billed but not yet paid by customers, in accordance with contract retainage provisions. At September 30, 2014 and December 31, 2013, contract retainage amounts that were unbilled and classified as unbilled receivables were $3.6 million and $4.3 million, respectively. These contract retainage amounts within trade receivables and unbilled receivables are expected to be collected within the following 12 months.

At September 30, 2014 and December 31, 2013, long-term unbilled receivables totaled $4.5 million and $4.7 million, respectively. These long-term unbilled receivables are classified within other long-term assets, as collection is not anticipated within the following 12 months. We had no long-term billed contract retainage receivables at September 30, 2014 and December 31, 2013, as we expect to collect all contract retainage receivables within the following 12 months.



Allowance for doubtful accounts activity	Three Months Ended September 30,						Nine Months Ended September 30,
	2014			2013			2014			2013
	(in thousands)
Beginning balance	$	7,355		$	6,948		$	8,368		$	7,372
Provision (release) of doubtful accounts, net	(356		)	1,290			(545		)	1,461
Accounts written-off	(233		)	(164		)	(1,023		)	(467		)
Effect of change in exchange rates	(242		)	153			(276		)	(139		)
Ending balance	$	6,524		$	8,227		$	6,524		$	8,227



Inventories	September 30, 2014		December 31, 2013
	(in thousands)
Materials	$	101,607	$	102,596
Work in process	11,694		13,770
Finished goods	77,388		61,101
Total inventories	$	190,689	$	177,467

Our inventory levels may vary from period to period as a result of our factory scheduling and the timing of contract fulfillments, which may include the buildup of materials in preparation for customer orders or finished goods for shipment.

Consigned inventory is held at third-party locations; however, we retain title to the inventory until it is purchased by the third-party. Consigned inventory, consisting of raw materials and finished goods, was $3.6 million and $6.4 million at September 30, 2014 and December 31, 2013, respectively.



Property, plant, and equipment, net	September 30, 2014			December 31, 2013
	(in thousands)
Machinery and equipment	$	307,098		$	309,525
Computers and software	101,861			99,654
Buildings, furniture, and improvements	139,681			145,926
Land	22,764			24,005
Construction in progress, including purchased equipment	16,730			14,257
Total cost	588,134			593,367
Accumulated depreciation	(365,780		)	(346,547		)
Property, plant, and equipment, net	$	222,354		$	246,820



Depreciation expense	Three Months Ended September 30,				Nine Months Ended September 30,
	2014		2013		2014		2013
	(in thousands)
Depreciation expense	$	13,691	$	14,330	$	42,118	$	42,370