Certain Balance Sheet Components Certain Balance Sheet Components (Tables)

12 Months Ended

Dec. 31, 2017

Balance Sheet Related Disclosures [Abstract]

Accounts Receivable, Net [Table Text Block]

Accounts receivable, net	December 31, 2017		December 31, 2016
	(in thousands)
Trade receivables (net of allowance of $3,957and $3,320)	$	369,047	$	299,870
Unbilled receivables	28,982		51,636
Total accounts receivable, net	$	398,029	$	351,506

Allowance for Credit Losses on Financing Receivables [Table Text Block]

Allowance for doubtful account activity	Year Ended December 31,
	2017			2016			2015
	(in thousands)
Beginning balance	$	3,320		$	5,949		$	6,195
Provision for doubtful accounts, net	1,656			60			1,025
Accounts written-off	(1,351		)	(2,422		)	(549		)
Effects of change in exchange rates	332			(267		)	(722		)
Ending balance	$	3,957		$	3,320		$	5,949

Inventories [Table Text Block]

Inventories	December 31, 2017		December 31, 2016
	(in thousands)
Materials	$	126,656	$	103,274
Work in process	9,863		7,925
Finished goods	57,316		51,850
Total inventories	$	193,835	$	163,049

Property, Plant, and Equipment [Table Text Block]

Property, plant, and equipment, net	December 31, 2017			December 31, 2016
	(in thousands)
Machinery and equipment	$	310,753		$	279,746
Computers and software	104,384			98,125
Buildings, furniture, and improvements	135,566			122,680
Land	18,433			17,179
Construction in progress, including purchased equipment	39,946			29,358
Total cost	609,082			547,088
Accumulated depreciation	(408,314		)	(370,630		)
Property, plant, and equipment, net	$	200,768		$	176,458

Depreciation Expense [Table Text Block]

Depreciation expense	Year Ended December 31,
	2017		2016		2015
	(in thousands)
Depreciation expense	$	42,430	$	43,206	$	44,320