Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities:
Net income (loss)	$ 4,507,000	$ (6,686,000)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	1,477,000	1,473,000
Amortization of right-of-use assets	297,000
Loss on disposal of fixed assets	721,000	142,000
Loss on impairment of intangible asset	281,000
Stock-based compensation expense	1,386,000	7,565,000
Deferred income taxes	(124,000)	(75,000)
Provision for inventory	381,000	3,246,000
Accretion to amortized cost of investments	(363,000)
Changes in operating assets and liabilities:
Accounts receivable	2,489,000	5,730,000
Inventories	(1,617,000)	(3,924,000)
Prepaid expenses, other current and long-term assets	(182,000)	509,000
Accounts payable	496,000	(180,000)
Lease liabilities	(269,000)
Accrued expenses, other current and long-term liabilities	(1,928,000)	3,270,000
Income taxes	910,000	(1,478,000)
Net cash provided by operating activities	8,462,000	9,592,000
Cash flows from investing activities:
Proceeds from maturity of investments	58,094,000	15,250,000
Purchase of investments	(58,981,000)	(12,500,000)
Purchase of property and equipment	(1,030,000)	(2,543,000)
Net cash (used in) provided by investing activities	(1,917,000)	207,000
Cash flows from financing activities:
Cash paid for tax withheld on vested restricted stock awards	(124,000)	(1,735,000)
Proceeds from exercise of equity awards	5,000	512,000
Net cash (used in) financing activities	(119,000)	(1,223,000)
Exchange rate impact on cash	46,000	(35,000)
Increase in cash and cash equivalents	6,472,000	8,541,000
Cash and cash equivalents at beginning of period	89,042,000	133,256,000
Cash and cash equivalents at end of period	95,514,000	141,797,000
Supplemental disclosure of cash flow information:
Right-of-use assets obtained in exchange for operating lease liabilities as of January 1, 2019	24,110
Purchases of property and equipment included in accounts payable and accrued expenses	$ 246,000	$ 207,000