CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net loss		$ (149,594)	$ (69,632)	$ (45,263)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Depreciation and amortization		44,595	50,396	59,293
Stock-based compensation		17,725	23,587	29,253
Provision for inventory obsolescence and revaluation		12,373	0	0
Loss on hedge accounting de-designation		1,235	0	0
Provision for bad debts		457	1,308	1,824
Loss on the disposition of property, equipment and other assets		5,274	2,282	0
Provision for deferred income taxes		(1,206)	(3,354)	(2,990)
Impairment of assets		55,484	1,728	1,998
Changes in operating accounts:
Accounts receivable		(6,052)	15,071	599
Inventories		(9,901)	18,447	(34,035)
Prepaid expenses and other current assets		(16,218)	9,150	40,922
Accounts payable		(6,653)	(16,846)	11,559
Deferred revenue and customer deposits		3,231	677	(2,383)
Accrued and other liabilities		28,286	(1,346)	(57,212)
All other operating activities		843	113	1,231
Net cash (used in) provided by operating activities		(20,121)	31,581	4,796
Cash flows from investing activities:
Purchases of property and equipment		(13,643)	(23,985)	(40,694)
Proceeds from sale of assets		1,554	1,620	333
Purchase of noncontrolling interest		(12,500)	(2,500)	0
Other investing activities		356	(2,007)	(1,466)
Net cash used in investing activities		(24,233)	(26,872)	(41,827)
Cash flows from financing activities:
Proceeds from revolving credit facilities		20,000	0
Payments on revolving credit facilities		(20,000)	0
Proceeds from borrowings		0	100,000	25,000
Repayment of borrowings/long term debt		(26,840)	(76,768)	0
Proceeds from issuance of common stock		24,702	0	0
Payments related to net-share settlement of stock based compensation		(5,138)	(3,194)	(7,367)
Payments on earnout consideration		0	0	(2,675)
Other financing activities		296	(1,338)	(694)
Net cash (used in) provided by financing activities		(6,980)	18,700	14,264
Effect of exchange rate changes on cash, cash equivalents and restricted cash		1,428	289	(3,145)
Net increase (decrease) in cash, cash equivalents and restricted cash		(49,906)	23,698	(25,912)
Cash, cash equivalents and restricted cash at the beginning of the period	[1]	134,617	110,919	136,831
Cash, cash equivalents and restricted cash at the end of the period	[1]	84,711	134,617	110,919
Supplemental cash flow information
Lease assets obtained in exchange for new lease liabilities (excludes adoption)		23,309	8,662	0
Cash interest payments		2,109	3,715	542
Cash income tax payments, net		3,706	10,722	8,964
Transfer of equipment from inventory to property and equipment, net	[2]	1,055	3,187	5,612
Transfer of equipment to inventory from property and equipment, net	[3]	0	32	2,563
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Purchase of noncontrolling interest	[4]	$ 0	$ (11,000)	$ 0

[1] The amounts for cash and cash equivalents shown above include restricted cash of $540, $952 and $921 as of December 31, 2020, 2019 and 2018, respectively, which were included in Other assets, net, and $9,161 as of December 31, 2020, which was included in Current assets held for sale 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 liabilities and Other liabilities on the consolidated balance sheets.