CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016
Cash flows from operating activities:
Net loss		$ (17,909)	$ (23,021)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization		30,575	30,435
Stock-based compensation		14,450	18,893
Provision for bad debts		166	2,677
Benefit of deferred income taxes		(1,580)	(2,201)
Changes in operating accounts, net of acquisitions:
Accounts receivable		5,549	30,375
Inventories		(9,766)	(16,153)
Prepaid expenses and other current assets		(2,532)	(2,463)
Accounts payable		4,343	(4,526)
Accrued and other current liabilities		(6,727)	(4,328)
Deferred revenue		8,032	8,198
All other operating activities		(6,209)	(6,846)
Net cash provided by operating activities		18,392	31,040
Cash flows from investing activities:
Cash paid for acquisitions, net of cash assumed		(34,291)
Purchases of property and equipment		(11,243)	(7,597)
Additions to license and patent costs		(571)	(790)
Other investing activities		(1,650)	(1,000)
Proceeds from disposition of property and equipment		271
Net cash used in investing activities		(47,484)	(9,387)
Cash flows from financing activities:
Payments on earnout consideration		(3,206)
Payments related to net-share settlement of stock-based compensation		(1,970)	(1,307)
Repayment of capital lease obligations		(290)	(524)
Net cash used in financing activities		(5,466)	(1,831)
Effect of exchange rate changes on cash and cash equivalents		3,602	783
Net (decrease) increase in cash and cash equivalents		(30,956)	20,605
Cash and cash equivalents at the beginning of the period		184,947	155,643
Cash and cash equivalents at the end of the period		153,991	176,248
Supplemental Cash Flow Information:
Cash interest payments		400	211
Cash income tax payments, net		3,367	5,933
Transfer of equipment from inventory to property and equipment, net	[1]	7,689	7,529
Transfer of equipment to inventory from property and equipment, net	[2]	907	$ 2,075
Stock issued for acquisitions		$ 3,208

[1] Inventory is transferred from inventory to property and equipment at cost when the Company requires additional machines for training or demonstration or for placement into on-demand manufacturing services locations.

[2] In general, an asset is transferred from property and equipment, net, into inventory at its net book value when the Company has identified a potential sale for a used machine.