CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 44,933	$ 46,946
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	11,531	11,321
Share–based compensation expense	7,755	7,899
Deferred income tax benefit	(323)	(1,015)
Other charges	41	26
Changes in operating assets and liabilities:
Receivables	(1,254)	(1,338)
Inventories	13,893	14,670
Prepaid expenses and other assets	3,602	2,945
Accounts payable	733	599
Accrued payroll and related benefits	(12,923)	(373)
Deferred revenue	2,633	1,891
Income taxes	5,794	(2,032)
Other accrued expenses and liabilities	(811)	(586)
Net cash provided by operating activities	75,604	80,953
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of short term investments	(18,651)	(30,196)
Proceeds from the sale and maturity of short term investments	11,643	12,080
Capital additions	(6,144)	(9,088)
Net cash used in investing activities	(13,152)	(27,204)
CASH FLOWS FROM FINANCING ACTIVITIES:
Exercise of stock options	1,939	4,144
Employee tax withholdings related to the vesting of equity awards	(1,916)	(1,596)
Repurchase of common shares for treasury	(26,304)	0
Repurchase and retirement of common shares	0	(2,285)
Payment of dividends	(22,667)	(15,987)
Net cash used in financing activities	(48,948)	(15,724)
NET INCREASE IN CASH AND CASH EQUIVALENTS	13,504	38,025
CASH AND CASH EQUIVALENTS, beginning of period	24,654	9,623
CASH AND CASH EQUIVALENTS, end of period	$ 38,158	$ 47,648