Certain Balance Sheet Components

9 Months Ended

Sep. 30, 2018

Balance Sheet Related Disclosures [Abstract]

Certain Balance Sheet Components

Certain Balance Sheet Components

A summary of accounts receivable from contracts with customers is as follows:

Accounts receivable, net	September 30, 2018		December 31, 2017
	(in thousands)
Trade receivables (net of allowance of $3,822 and $3,957)	$	422,567	$	369,047
Unbilled receivables	27,025		28,982
Total accounts receivable, net	$	449,592	$	398,029

Allowance for doubtful accounts activity	Three Months Ended September 30,						Nine Months Ended September 30,
	2018			2017			2018			2017
	(in thousands)
Beginning balance	$	4,552		$	3,502		$	3,957		$	3,320
Provision (recovery) for doubtful accounts, net	(105		)	769			1,149			1,513
Accounts written-off	(624		)	(310		)	(1,129		)	(1,115		)
Effect of change in exchange rates	(1		)	30			(155		)	273
Ending balance	$	3,822		$	3,991		$	3,822		$	3,991

Inventories	September 30, 2018		December 31, 2017
	(in thousands)
Materials	$	128,744	$	126,656
Work in process	8,595		9,863
Finished goods	70,699		57,316
Total inventories	$	208,038	$	193,835

Property, plant, and equipment, net	September 30, 2018			December 31, 2017
	(in thousands)
Machinery and equipment	$	318,218		$	310,753
Computers and software	112,681			104,384
Buildings, furniture, and improvements	149,934			135,566
Land	15,463			18,433
Construction in progress, including purchased equipment	41,423			39,946
Total cost	637,719			609,082
Accumulated depreciation	(416,924		)	(408,314		)
Property, plant, and equipment, net	$	220,795		$	200,768

Depreciation expense	Three Months Ended September 30,				Nine Months Ended September 30,
	2018		2017		2018		2017
	(in thousands)
Depreciation expense	$	12,489	$	10,907	$	38,729	$	30,856