Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities:
Net income (loss)	$ (6,686)	$ 5,493
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	1,473	1,014
Loss on disposal of fixed assets	142
Stock-based compensation expense	7,565	1,182
Deferred income taxes	(75)	385
Provision for inventory	3,246	264
Changes in operating assets and liabilities:
Accounts receivable	5,730	6,601
Inventories	(3,924)	(431)
Prepaid expenses, other current and long-term assets	509	744
Accounts payable	(180)	2,020
Accrued expenses, other current and long-term liabilities	3,270	(1,807)
Income taxes	(1,478)	(5)
Net cash provided by operating activities	9,592	15,460
Cash flows from investing activities:
Proceeds from maturity of investments	15,250	12,500
Purchase of investments	(12,500)	(11,250)
Purchase of property and equipment	(2,543)	(1,675)
Net cash provided by (used in) investing activities	207	(425)
Cash flows from financing activities:
Cash paid for tax withheld on vested restricted stock awards	(1,735)
Proceeds from exercise of equity awards	512	41
Net cash (used in) provided by financing activities	(1,223)	41
Exchange rate impact on cash	(35)	31
Increase in cash and cash equivalents	8,541	15,107
Cash and cash equivalents at beginning of period	133,256	104,261
Cash and cash equivalents at end of period	141,797	119,368
Supplemental disclosure of cash flow information:
Purchases of property and equipment included in accounts payable and accrued expenses	$ 207	$ 2,081