CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities:
Net loss	$ (8,382)	$ (4,821)
Adjustments to reconcile net loss to net cash flows used in operating activities:
Share-based compensation	3,244	3,349
Depreciation	1,161	1,506
Amortization of intangible assets	239	271
Amortization of deferred financing costs	415	668
Non-cash lease expenses	237	239
Accretion of asset retirement obligation	17	0
Loss on fixed asset disposal	236	0
Increase (decrease) in cash resulting from changes in:
Accounts receivable	3	395
Inventory	(1,221)	(143)
Prepaid expenses	910	1,430
Income taxes	54	(10,711)
Other assets	319	812
Accounts payable	(936)	1,046
Accrued compensation	(2,314)	(4,186)
Accrued expenses	(484)	(2,845)
Other liabilities	(177)	709
Net cash flows used in operating activities	(6,679)	(12,281)
Cash flows from investing activities:
Purchases of equipment	(1,941)	(1,011)
Principal payments from note receivable	15	0
Patent application costs	(153)	(75)
Net cash flows used in investing activities	(2,079)	(1,086)
Cash flows from financing activities:
Proceeds from exercise of stock options	915	298
Stock repurchased for tax withholdings on vesting of restricted stock	(3,216)	(1,538)
Principal payments on finance lease	(7)	0
Repayment of term loans	0	(937)
Net cash flows used in financing activities	(2,308)	(2,177)
Net change in cash	(11,066)	(15,544)
Cash and cash equivalents, beginning of period	95,812	69,069
Cash and cash equivalents, end of period	$ 84,746	$ 53,525