Certain Balance Sheet Components (Tables)

6 Months Ended

Jun. 30, 2018

Balance Sheet Related Disclosures [Abstract]

Accounts Receivable, Net

Accounts receivable, net	June 30, 2018		December 31, 2017
	(in thousands)
Trade receivables (net of allowance of $4,552 and $3,957)	$	412,848	$	369,047
Unbilled receivables	30,546		28,982
Total accounts receivable, net	$	443,394	$	398,029

Allowance for Credit Losses on Financing Receivables

Allowance for doubtful accounts activity	Three Months Ended June 30,						Six Months Ended June 30,
	2018			2017			2018			2017
	(in thousands)
Beginning balance	$	4,774		$	3,424		$	3,957		$	3,320
Provision for doubtful accounts, net	334			441			1,254			744
Accounts written-off	(247		)	(475		)	(505		)	(805		)
Effect of change in exchange rates	(309		)	112			(154		)	243
Ending balance	$	4,552		$	3,502		$	4,552		$	3,502

Inventories

Inventories	June 30, 2018		December 31, 2017
	(in thousands)
Materials	$	125,917	$	126,656
Work in process	8,953		9,863
Finished goods	60,186		57,316
Total inventories	$	195,056	$	193,835

Property, Plant, and Equipment, Net

Property, plant, and equipment, net	June 30, 2018			December 31, 2017
	(in thousands)
Machinery and equipment	$	310,855		$	310,753
Computers and software	110,758			104,384
Buildings, furniture, and improvements	145,893			135,566
Land	15,457			18,433
Construction in progress, including purchased equipment	45,370			39,946
Total cost	628,333			609,082
Accumulated depreciation	(404,898		)	(408,314		)
Property, plant, and equipment, net	$	223,435		$	200,768

Depreciation Expense

Depreciation expense	Three Months Ended June 30,				Six Months Ended June 30,
	2018		2017		2018		2017
	(in thousands)
Depreciation expense	$	12,908	$	10,120	$	26,240	$	19,949