Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Cash flows from operating activities:
Net income	$ 16,862	$ 15,510
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	2,022	1,901
Stock-based compensation expense	2,465	1,478
Deferred income taxes	589	(252)
Provision for doubtful accounts	(1)	52
Provision for inventory	287	181
Changes in operating assets and liabilities:
Accounts receivable	(2,449)	(2,932)
Inventories	(1,741)	(2,438)
Prepaid expenses, other current and long-term assets	(155)	186
Accounts payable	2,362	(4,252)
Accrued expenses and other current liabilities	(182)	446
Income taxes	2,303	(3,169)
Other long-term liabilities	(631)	351
Net cash provided by operating activities	21,731	7,062
Cash flows from investing activities:
Proceeds from maturity of investments	20,000	27,750
Purchase of investments	(24,500)	(22,499)
Purchase of property and equipment	(3,917)	(9,869)
Net cash used in investing activities	(8,417)	(4,618)
Cash flows from financing activities:
Repurchases of common stock	0	(25,000)
Proceeds from exercise of equity awards	209	922
Net cash provided by (used in) financing activities	209	(24,078)
Exchange rate impact on cash	90	52
Increase (decrease) in cash and cash equivalents	13,613	(21,582)
Cash and cash equivalents at beginning of period	104,261	110,707
Cash and cash equivalents at end of period	117,874	89,125
Non-cash Investing Activities:
Purchases of property and equipment included in accounts payable and accrued expenses	1,193	2,128
Build-to-suit lease agreement	$ 0	$ 482