Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities:
Net income	$ 13,942	$ 3,405
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	2,943	2,920
Non-cash operating lease cost	591
Loss on disposal of fixed assets	721	172
Loss on impairment of intangible asset	281
Stock-based compensation expense	2,829	8,887
Deferred income taxes	120	63
Provision for doubtful accounts		(6)
Provision for inventory	601	3,993
Accretion to amortized cost of investments	(757)
Changes in operating assets and liabilities:
Accounts receivable	(2,293)	1,926
Inventories	(3,033)	(5,990)
Prepaid expenses, other current and long-term assets	356	790
Accounts payable	(906)	(194)
Operating lease liabilities	(534)
Accrued expenses, other current and long-term liabilities	(1,300)	(100)
Income taxes	371	(1,803)
Net cash provided by operating activities	13,932	14,063
Cash flows from investing activities:
Proceeds from maturity of investments	72,594	24,750
Purchase of investments	(73,896)	(14,000)
Purchase of property and equipment	(2,131)	(3,283)
Net cash (used in) provided by investing activities	(3,433)	7,467
Cash flows from financing activities:
Repurchases of common stock	(30,000)	(30,000)
Cash paid for tax withheld on vested restricted stock awards	(125)	(1,735)
Proceeds from exercise of equity awards	6	2,886
Net cash used in financing activities	(30,119)	(28,849)
Exchange rate impact on cash	(15)	110
Decrease in cash and cash equivalents	(19,635)	(7,209)
Cash and cash equivalents at beginning of period	89,042	133,256
Cash and cash equivalents at end of period	69,407	126,047
Supplemental disclosure of cash flow information:
Right-of-use assets obtained in exchange for operating lease liabilities as of January 1, 2019	24,110
Non-cash activities:
Purchases of property and equipment included in accounts payable and accrued expenses	$ 211	$ 462