Certain Balance Sheet Components



Accounts receivable, net	December 31, 2014		December 31, 2013
	(in thousands)
Trade receivables (net of allowance of $6,195 and $8,368)	$	312,302	$	328,240
Unbilled receivables	36,087		28,469
Total accounts receivable, net	$	348,389	$	356,709

At December 31, 2014 and 2013, $4.7 million and $3.2 million were recorded within trade receivables as billed but not yet paid by customers in accordance with contract retainage provisions. At December 31, 2014 and 2013, contract retainage amounts that were unbilled and classified as unbilled receivables were $4.0 million and $4.3 million. These contract retainage amounts within trade receivables and unbilled receivables are expected to be collected within the following 12 months.

At December 31, 2014 and 2013, long-term unbilled receivables totaled $4.3 million and $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 December 31, 2014, as we expect to collect all contract retainage receivables within the following 12 months.



Allowance for doubtful account activity	Year Ended December 31,
	2014			2013
	(in thousands)
Beginning balance	$	8,368		$	7,372
Provision for doubtful accounts, net	308			1,740
Accounts written-off	(1,955		)	(636		)
Effects of change in exchange rates	(526		)	(108		)
Ending balance	$	6,195		$	8,368



Inventories	December 31, 2014		December 31, 2013
	(in thousands)
Materials	$	90,557	$	102,596
Work in process	8,991		13,770
Finished goods	54,956		61,101
Total inventories	$	154,504	$	177,467

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

Consigned inventory is held at third-party locations; however, we retain title to the inventory until purchased by the third-party. Consigned inventory, consisting of raw materials and finished goods, was $2.5 million and $6.4 million at December 31, 2014 and 2013, respectively.



Property, plant, and equipment, net	December 31, 2014			December 31, 2013
	(in thousands)
Machinery and equipment	$	287,448		$	309,525
Computers and software	100,212			99,654
Buildings, furniture, and improvements	134,461			145,926
Land	21,186			24,005
Construction in progress, including purchased equipment	21,007			14,257
Total cost	564,314			593,367
Accumulated depreciation	(356,525		)	(346,547		)
Property, plant, and equipment, net	$	207,789		$	246,820



Depreciation expense	Year Ended December 31,
	2014		2013		2012
	(in thousands)
Depreciation expense	$	54,759	$	56,826	$	61,661