Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash flows from operating activities:
Net income	$ 3,405	$ 16,862
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	2,920	2,022
Loss on disposal of fixed assets	172
Stock-based compensation expense	8,887	2,465
Deferred income taxes	63	589
Provision for doubtful accounts	(6)	(1)
Provision for inventory	3,993	287
Changes in operating assets and liabilities:
Accounts receivable	1,926	(2,449)
Inventories	(5,990)	(1,741)
Prepaid expenses, other current and long-term assets	790	(155)
Accounts payable	(194)	2,362
Accrued expenses, other current and long-term liabilities	(100)	(813)
Income taxes	(1,803)	2,303
Net cash provided by operating activities	14,063	21,731
Cash flows from investing activities:
Proceeds from maturity of investments	24,750	20,000
Purchase of investments	(14,000)	(24,500)
Purchase of property and equipment	(3,283)	(3,917)
Net cash provided by (used in) investing activities	7,467	(8,417)
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	209
Net cash (used in) provided by financing activities	(28,849)	209
Exchange rate impact on cash	110	90
(Decrease) Increase in cash and cash equivalents	(7,209)	13,613
Cash and cash equivalents at beginning of period	133,256	104,261
Cash and cash equivalents at end of period	126,047	117,874
Supplemental disclosure of cash flow information:
Purchases of property and equipment included in accounts payable and accrued expenses	$ 462	$ 1,193