Certain Balance Sheet Components



Accounts receivable, net	June 30, 2014		December 31, 2013
	(in thousands)
Trade receivables (net of allowance of $7,355 and $8,368)	$	341,937	$	328,240
Unbilled receivables	27,536		28,469
Total accounts receivable, net	$	369,473	$	356,709

At June 30, 2014 and December 31, 2013, $4.3 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 June 30, 2014 and December 31, 2013, contract retainage amounts that were unbilled and classified as unbilled receivables were $3.1 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 June 30, 2014 and December 31, 2013, long-term unbilled receivables totaled $4.7 million. 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 June 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 June 30,						Six Months Ended June 30,
	2014			2013			2014			2013
	(in thousands)
Beginning balance	$	8,758		$	6,144		$	8,368		$	7,372
Provision (release) of doubtful accounts, net	(795		)	1,075			(189		)	171
Accounts written-off	(558		)	(198		)	(790		)	(303		)
Effect of change in exchange rates	(50		)	(73		)	(34		)	(292		)
Ending balance	$	7,355		$	6,948		$	7,355		$	6,948



Inventories	June 30, 2014		December 31, 2013
	(in thousands)
Materials	$	106,842	$	102,596
Work in process	13,981		13,770
Finished goods	71,590		61,101
Total inventories	$	192,413	$	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 $3.4 million and $6.4 million at June 30, 2014 and December 31, 2013, respectively.



Property, plant, and equipment, net	June 30, 2014			December 31, 2013
	(in thousands)
Machinery and equipment	$	312,657		$	309,525
Computers and software	102,395			99,654
Buildings, furniture, and improvements	146,069			145,926
Land	23,957			24,005
Construction in progress, including purchased equipment	18,123			14,257
Total cost	603,201			593,367
Accumulated depreciation	(368,361		)	(346,547		)
Property, plant, and equipment, net	$	234,840		$	246,820



Depreciation expense	Three Months Ended June 30,				Six Months Ended June 30,
	2014		2013		2014		2013
	(in thousands)
Depreciation expense	$	13,905	$	14,027	$	28,427	$	28,040