Certain Balance Sheet Components



Accounts receivable, net	December 31, 2013		December 31, 2012
	(in thousands)
Trade receivables (net of allowance of $8,368 and $7,372)	$	328,240	$	329,352
Unbilled receivables	28,469		45,974
Total accounts receivable, net	$	356,709	$	375,326

At December 31, 2013 and 2012, $3.2 million and $20.0 million were recorded within trade receivables as billed but not yet paid by customers in accordance with contract retainage provisions. At December 31, 2013 and 2012, contract retainage amounts that were unbilled and classified as unbilled receivables were $4.3 million and $11.1 million. These contract retainage amounts within trade receivables and unbilled receivables are expected to be collected within the following 12 months.

At 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 December 31, 2013, as we expect to collect all contract retainage receivables within the following 12 months. We had no long-term unbilled receivables or long-term billed contract retainage receivables at December 31, 2012.



Allowance for doubtful account activity	Year Ended December 31,
	2013			2012
	(in thousands)
Beginning balance	$	7,372		$	6,049
Provision of doubtful accounts, net	1,740			1,851
Accounts written-off	(636		)	(595		)
Effects of change in exchange rates	(108		)	67
Ending balance	$	8,368		$	7,372



Inventories	December 31, 2013		December 31, 2012
	(in thousands)
Materials	$	102,596	$	92,038
Work in process	13,770		12,568
Finished goods	61,101		66,113
Total inventories	$	177,467	$	170,719

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 $6.4 million and $5.0 million at December 31, 2013 and 2012, respectively.



Property, plant, and equipment, net	December 31, 2013			December 31, 2012
	(in thousands)
Machinery and equipment	$	309,525		$	287,791
Computers and software	99,654			84,980
Buildings, furniture, and improvements	145,926			146,191
Land	24,005			25,318
Construction in progress, including purchased equipment	14,257			26,097
Total cost	593,367			570,377
Accumulated depreciation	(346,547		)	(315,165		)
Property, plant, and equipment, net	$	246,820		$	255,212



Depreciation expense	Year Ended December 31,
	2013		2012		2011
	(in thousands)
Depreciation expense	$	56,826	$	61,661	$	66,072