CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities:
Net loss		$ (69,632)	$ (45,263)	$ (65,323)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization		50,396	59,293	62,041
Stock-based compensation		23,587	29,253	27,260
Lower of cost or market adjustment		0	0	12,883
Provision for bad debts		1,308	1,824	1,051
Loss on the disposition of property, equipment and other assets		2,282	0	0
Provision for deferred income taxes		(3,354)	(2,990)	(5,567)
Impairment of assets		1,728	1,998	2,427
Changes in operating accounts:
Accounts receivable		15,071	599	3,987
Inventories		18,447	(34,035)	(17,716)
Prepaid expenses and other current assets		9,150	40,922	(49,834)
Accounts payable		(16,846)	11,559	12,448
Deferred revenue and customer deposits		677	(2,383)	(121)
Accrued and other current liabilities		960	(47,851)	50,330
All other operating activities		(2,193)	(8,130)	(7,739)
Net cash provided by operating activities		31,581	4,796	26,127
Cash flows from investing activities:
Purchases of property and equipment		(23,985)	(40,694)	(30,881)
Cash paid for acquisition		0	0	(34,291)
Proceeds from sale of assets		1,620	333	273
Purchase of noncontrolling interest		(2,500)	0	(2,250)
Other investing activities		(2,007)	(1,466)	(3,510)
Net cash used in investing activities		(26,872)	(41,827)	(70,659)
Cash flows from financing activities:
Proceeds from borrowings		100,000	25,000	0
Repayment of borrowings/long term debt		(76,768)	0	0
Payments related to net-share settlement of stock based compensation		(3,194)	(7,367)	(5,545)
Payments on earnout consideration		0	(2,675)	(3,206)
Other financing activities		(1,338)	(694)	(437)
Net cash provided by (used in) financing activities		18,700	14,264	(9,188)
Effect of exchange rate changes on cash, cash equivalents and restricted cash		289	(3,145)	5,303
Net increase (decrease) in cash, cash equivalents and restricted cash		23,698	(25,912)	(48,417)
Cash, cash equivalents and restricted cash at the beginning of the period	[1]	110,919	136,831	185,248
Cash, cash equivalents and restricted cash at the end of the period	[1]	134,617	110,919	136,831
Supplemental cash flow information
Cash interest payments		3,715	542	503
Cash income tax payments, net		10,722	8,964	6,339
Transfer of equipment from inventory to property and equipment, net	[2]	3,187	5,612	9,881
Transfer of equipment to inventory from property and equipment, net	[3]	32	2,563	378
Issuance of stock for acquisitions		0	0	3,208
Purchase of noncontrolling interest	[4]	$ (11,000)	$ 0	$ 0

[1] The amounts for cash and cash equivalents shown above include restricted cash of $952, $921 and $487 as of December 31, 2019, 2018 and 2017, respectively, which were included in Other assets, net, in the consolidated balance sheets.

[2] Inventory is transferred from inventory to property and equipment at cost when we require additional machines for training or demonstration or for placement into on demand manufacturing services locations.

[3] In general, an asset is transferred from Property and equipment, net, into inventory at its net book value when we have identified a potential sale for a used machine.

[4] Purchase of noncontrolling interest to be paid in installments over a four-year period recorded to Accrued and other current liabilities and Other liabilities on the consolidated balance sheets.