CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 46,946	$ 26,619
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	11,321	10,160
Loss on disposal of fixed assets	0	104
Share–based compensation expense	7,899	5,134
Deferred income tax (benefit) expense	(1,015)	1,609
Other charges	26	2
Changes in operating assets and liabilities:
Receivables	(1,338)	6,662
Inventories	14,670	11,102
Other assets	2,945	3,290
Accounts payable	599	(6,698)
Accrued payroll and related benefits	(373)	(273)
Deferred revenue	1,891	193
Income taxes	(2,032)	(1,153)
Other accrued expenses and liabilities	(586)	(827)
Net cash provided by operating activities	80,953	55,924
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of short term investments	(30,196)	(14,067)
Proceeds from sales of short term investments	12,080	4,047
Capital additions	(9,088)	(10,444)
Net cash used in investing activities	(27,204)	(20,464)
CASH FLOWS FROM FINANCING ACTIVITIES:
Exercise of stock options	4,144	1,839
Employee tax withholdings related to the vesting of equity awards	(1,596)	(2,652)
Excess tax benefits from share-based compensation	0	1,766
Repurchase and retirement of common stock	(2,285)	0
Payment of dividends	(15,987)	(15,587)
Net cash used in financing activities	(15,724)	(14,634)
NET INCREASE IN CASH AND CASH EQUIVALENTS	38,025	20,826
CASH AND CASH EQUIVALENTS, beginning of period	9,623	6,191
CASH AND CASH EQUIVALENTS, end of period	$ 47,648	$ 27,017