Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Cash flows from operating activities:
Net income	$ 23,142	$ 11,004
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	4,459	4,433
Non-cash operating lease cost	880
Loss on disposal of fixed assets	927	172
Loss on impairment of intangible asset	303
Stock-based compensation expense	4,140	10,064
Deferred income taxes	941	(1,205)
Provision (recovery) for doubtful accounts	(450)	(87)
Provision for inventory	1,062	4,073
Accretion to amortized cost of investments	(1,075)
Changes in operating assets and liabilities:
Accounts receivable	(2,751)	3,136
Inventories	(6,600)	(5,891)
Prepaid expenses, other current and long-term assets	440	1,304
Accounts payable	(335)	(2,449)
Operating lease liabilities	(796)
Accrued expenses, other current and long-term liabilities	(681)	509
Income taxes	377	(158)
Net cash provided by operating activities	23,983	24,905
Cash flows from investing activities:
Proceeds from maturity of investments	87,594	34,500
Purchase of investments	(86,368)	(77,683)
Purchase of property and equipment	(2,559)	(4,493)
Net cash (used in) provided by investing activities	(1,333)	(47,676)
Cash flows from financing activities:
Repurchases of common stock	(30,000)	(30,000)
Cash paid for tax withheld on vested restricted stock awards	(245)	(1,735)
Proceeds from exercise of equity awards	21,825	2,886
Net cash used in financing activities	(8,420)	(28,849)
Exchange rate impact on cash	109	189
Decrease in cash and cash equivalents	14,339	(51,431)
Cash and cash equivalents at beginning of period	89,042	133,256
Cash and cash equivalents at end of period	103,381	81,825
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	$ 132	$ 197