CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities:
Net (loss) income	$ (13,273)	$ 4,619
Adjustments to reconcile net (loss) income to net cash from operating activities:
Share-based compensation	3,014	4,931
Depreciation	1,695	1,221
Amortization of intangible assets	233	252
Amortization of discount on notes receivable	0	(51)
Amortization of deferred financing costs	0	43
Non-cash lease expenses	269
Loss on fixed asset disposal	1	0
Impairment of intangible assets	1,258	0
Change in deferred income taxes	0	(1,267)
Increase (decrease) in cash resulting from changes in:
Inventory	(442)	(157)
Prepaid expenses	2,053	(266)
Income tax receivable	(12)	(159)
Other current assets	(1,612)	(1,041)
Accounts payable	(4,173)	5,075
Accrued compensation	(7,501)	(5,302)
Accrued expenses	3,895	2,412
Other liabilities	(665)	(134)
Net cash flows (used in) provided by operating activities	(15,260)	10,176
Cash flows from investing activities:
Purchases of equipment	(648)	(3,069)
Principal payments from note receivable	389	0
Patent application costs	(174)	(38)
Net cash flows used in investing activities	(433)	(3,107)
Cash flows from financing activities:
Proceeds from exercise of stock options	0	3,554
Shares repurchased under repurchase plan	0	(7,572)
Shares repurchased for tax withholdings on vesting of restricted stock	(1,044)	(4,073)
Net cash flows used in financing activities	(1,044)	(8,091)
Net change in cash	(16,737)	(1,022)
Cash and cash equivalents, beginning of period	45,118	27,476
Cash and cash equivalents, end of period	$ 28,381	$ 26,454