Certain Balance Sheet Components



Accounts receivable, net	March 31, 2015		December 31, 2014
	(in thousands)
Trade receivables (net of allowance of $5,939 and $6,195)	$	284,218	$	312,302
Unbilled receivables	40,488		36,087
Total accounts receivable, net	$	324,706	$	348,389

At March 31, 2015 and December 31, 2014, $2.8 million and $4.7 million, respectively, were recorded within trade receivables as billed but not yet paid by customers, in accordance with contract retainage provisions. At March 31, 2015 and December 31, 2014, contract retainage amounts that were unbilled and classified as unbilled receivables were $3.3 million and $4.0 million, respectively. These contract retainage amounts within trade receivables and unbilled receivables are expected to be collected within the following 12 months.

At March 31, 2015 and December 31, 2014, long-term unbilled receivables totaled $4.0 million and $4.3 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 March 31, 2015 and December 31, 2014.



Allowance for doubtful accounts activity	Three Months Ended March 31,
	2015			2014
	(in thousands)
Beginning balance	$	6,195		$	8,368
Provision for doubtful accounts, net	269			606
Accounts written-off	(16		)	(232		)
Effect of change in exchange rates	(509		)	16
Ending balance	$	5,939		$	8,758



Inventories	March 31, 2015		December 31, 2014
	(in thousands)
Materials	$	95,277	$	90,557
Work in process	9,374		8,991
Finished goods	63,510		54,956
Total inventories	$	168,161	$	154,504

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 $3.1 million and $2.5 million at March 31, 2015 and December 31, 2014, respectively.



Property, plant, and equipment, net	March 31, 2015			December 31, 2014
	(in thousands)
Machinery and equipment	$	276,903		$	287,448
Computers and software	98,403			100,212
Buildings, furniture, and improvements	129,321			134,461
Land	20,793			21,186
Construction in progress, including purchased equipment	22,691			21,007
Total cost	548,111			564,314
Accumulated depreciation	(355,330		)	(356,525		)
Property, plant, and equipment, net	$	192,781		$	207,789

Assets of our international subsidiaries are recorded in their respective functional currency; therefore, the carrying amounts of these assets increase or decrease, with a corresponding change in accumulated OCI, due to changes in foreign currency exchange rates. In addition, depreciation expense is impacted by the fluctuations in foreign exchange rates.



Depreciation expense	Three Months Ended March 31,
	2015		2014
	(in thousands)
Depreciation expense	$	11,366	$	14,522