Certain Balance Sheet Components



Accounts receivable, net	March 31, 2016		December 31, 2015
	(in thousands)
Trade receivables (net of allowance of $4,541 and $5,949)	$	321,814	$	298,550
Unbilled receivables	46,618		32,345
Total accounts receivable, net	$	368,432	$	330,895

At March 31, 2016 and December 31, 2015, $1.5 million and $0.7 million, respectively, were recorded as contract retainage receivables within trade receivables, in accordance with contract retainage provisions. At March 31, 2016 and December 31, 2015, contract retainage receivables that were unbilled and classified as unbilled receivables were $4.6 million and $3.5 million, respectively. These contract retainage receivables within trade receivables and unbilled receivables are expected to be collected within the following 12 months.

At March 31, 2016 and December 31, 2015, long-term billed contract retainage receivables were $0.4 million. At March 31, 2016 and December 31, 2015, long-term unbilled contract retainage receivables were $3.8 million and $3.6 million, respectively. These long-term billed and unbilled contract retainage receivables are classified within other long-term assets, as collection is not anticipated within the following 12 months. We consider whether collectability of such retainage is reasonably assured in connection with our overall assessment of the collectability of amounts due or that will become due under our contracts.



Allowance for doubtful accounts activity	Three Months Ended March 31,
	2016			2015
	(in thousands)
Beginning balance	$	5,949		$	6,195
Provision (release) for doubtful accounts, net	(8		)	269
Accounts written-off	(1,478		)	(16		)
Effect of change in exchange rates	78			(509		)
Ending balance	$	4,541		$	5,939



Inventories	March 31, 2016		December 31, 2015
	(in thousands)
Materials	$	115,331	$	111,191
Work in process	10,836		9,400
Finished goods	62,843		69,874
Total inventories	$	189,010	$	190,465

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 $2.3 million and $2.6 million at March 31, 2016 and December 31, 2015, respectively.



Property, plant, and equipment, net	March 31, 2016			December 31, 2015
	(in thousands)
Machinery and equipment	$	289,411		$	289,015
Computers and software	104,795			104,310
Buildings, furniture, and improvements	128,437			127,531
Land	20,009			19,882
Construction in progress, including purchased equipment	32,567			32,639
Total cost	575,219			573,377
Accumulated depreciation	(385,215		)	(383,121		)
Property, plant, and equipment, net	$	190,004		$	190,256



Depreciation expense	Three Months Ended March 31,
	2016		2015
	(in thousands)
Depreciation expense	$	10,464	$	11,382