Certain Balance Sheet Components (Tables)

3 Months Ended

Mar. 31, 2018

Balance Sheet Related Disclosures [Abstract]

Accounts Receivable, Net [Table Text Block]

	March 31, 2018		December 31, 2017
	(in thousands)
Trade receivables (net of allowance of $4,774 and $3,957)	$	448,211	$	369,047
Unbilled receivables	33,178		28,982
Total accounts receivable, net	$	481,389	$	398,029

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

Allowance for doubtful accounts activity	Three Months Ended March 31,
	2018			2017
	(in thousands)
Beginning balance	$	3,957		$	3,320
Provision for doubtful accounts, net	920			303
Accounts written-off	(258		)	(330		)
Effect of change in exchange rates	155			131
Ending balance	$	4,774		$	3,424

Inventories [Table Text Block]

Inventories	March 31, 2018		December 31, 2017
	(in thousands)
Materials	$	132,990	$	126,656
Work in process	8,700		9,863
Finished goods	67,683		57,316
Total inventories	$	209,373	$	193,835

Property, Plant, and Equipment, Net [Table Text Block]

Property, plant, and equipment, net	March 31, 2018			December 31, 2017
	(in thousands)
Machinery and equipment	$	332,055		$	310,753
Computers and software	111,227			104,384
Buildings, furniture, and improvements	150,049			135,566
Land	16,638			18,433
Construction in progress, including purchased equipment	41,959			39,946
Total cost	651,928			609,082
Accumulated depreciation	(417,004		)	(408,314		)
Property, plant, and equipment, net	$	234,924		$	200,768

Depreciation Expense [Table Text Block]

Depreciation expense	Three Months Ended March 31,
	2018		2017
	(in thousands)
Depreciation expense	$	13,332	$	9,829