Certain Balance Sheet Components (Tables)

9 Months Ended

Sep. 30, 2018

Balance Sheet Related Disclosures [Abstract]

Accounts Receivable, Net

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 Credit Losses on Financing Receivables

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

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

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

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