Certain Balance Sheet Components (Tables)

12 Months Ended

Dec. 31, 2018

Balance Sheet Related Disclosures [Abstract]

Accounts Receivable, Net

Accounts receivable, net	December 31, 2018		December 31, 2017
	(in thousands)
Trade receivables (net of allowance of $6,331 and $3,957)	$	416,503	$	369,047
Unbilled receivables	20,658		28,982
Total accounts receivable, net	$	437,161	$	398,029

Allowance for Credit Losses on Financing Receivables

Allowance for doubtful account activity	Year Ended December 31,
	2018			2017			2016
	(in thousands)
Beginning balance	$	3,957		$	3,320		$	5,949
Provision for doubtful accounts, net	3,874			1,656			60
Accounts written-off	(1,281		)	(1,351		)	(2,422		)
Effects of change in exchange rates	(219		)	332			(267		)
Ending balance	$	6,331		$	3,957		$	3,320

Inventories

Inventories	December 31, 2018		December 31, 2017
	(in thousands)
Materials	$	133,398	$	126,656
Work in process	9,744		9,863
Finished goods	77,532		57,316
Total inventories	$	220,674	$	193,835

Property, Plant, and Equipment

Property, plant, and equipment, net	December 31, 2018			December 31, 2017
	(in thousands)
Machinery and equipment	$	315,974		$	310,753
Computers and software	104,290			104,384
Buildings, furniture, and improvements	146,071			135,566
Land	14,980			18,433
Construction in progress, including purchased equipment	49,682			39,946
Total cost	630,997			609,082
Accumulated depreciation	(404,446		)	(408,314		)
Property, plant, and equipment, net	$	226,551		$	200,768

Depreciation Expense

Depreciation expense	Year Ended December 31,
	2018		2017		2016
	(in thousands)
Depreciation expense	$	50,784	$	42,430	$	43,206