Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net income	$ 11,004	$ 23,749
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	4,433	3,224
Loss on disposal of fixed assets	172
Stock-based compensation expense	10,064	3,940
Deferred income taxes	(1,205)	943
Provision for doubtful accounts	(87)	(1)
Provision for inventory	4,073	609
Changes in operating assets and liabilities:
Accounts receivable	3,136	4,388
Inventories	(5,891)	(4,668)
Prepaid expenses, other current and long-term assets	1,304	(922)
Accounts payable	(2,449)	2,030
Accrued expenses, other current and long-term liabilities	509	(106)
Income taxes	(158)	645
Net cash provided by operating activities	24,905	33,831
Cash flows from investing activities:
Proceeds from maturity of investments	34,500	31,250
Purchase of investments	(77,683)	(36,500)
Purchase of property and equipment	(4,493)	(6,506)
Net cash (used in) investing activities	(47,676)	(11,756)
Cash flows from financing activities:
Repurchases of common stock	(30,000)
Cash paid for tax withheld on vested restricted stock awards	(1,735)
Proceeds from exercise of equity awards	2,886	310
Net cash (used in) provided by financing activities	(28,849)	310
Exchange rate impact on cash	189	314
(Decrease) Increase in cash and cash equivalents	(51,431)	22,699
Cash and cash equivalents at beginning of period	133,256	104,261
Cash and cash equivalents at end of period	81,825	126,960
Supplemental disclosure of cash flow information:
Purchases of property and equipment included in accounts payable and accrued expenses	$ 197	$ 1,208