CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
CURRENT ASSETS:
Cash and cash equivalents	$ 121,327	$ 93,655
Short-term marketable securities	136,370	189,236
Accounts receivable, net of allowances for doubtful accounts of $739 and $734 in 2018 and 2017, respectively	17,727	16,798
Inventories	63,208	57,087
Prepaid expenses and other current assets	11,003	7,758
Total current assets	349,635	364,534
PROPERTY AND EQUIPMENT, net	109,871	111,705
INTANGIBLE ASSETS, net	25,071	25,419
GOODWILL	91,849	91,849
DEFERRED TAX ASSETS	2,506	2,364
OTHER ASSETS	25,502	25,203
Total assets	604,434	621,074
CURRENT LIABILITIES:
Accounts payable	30,991	33,211
Accrued payroll and related expenses	10,564	12,064
Taxes payable	2,183	1,767
Other accrued liabilities	4,427	4,009
Total current liabilities	48,165	51,051
LONG-TERM INCOME TAXES PAYABLE	18,138	18,259
DEFERRED TAX LIABILITIES	140	138
OTHER LIABILITIES	4,159	3,944
Total liabilities	70,602	73,392
COMMITMENTS AND CONTINGENCIES (Notes 11, 12 and 13)
STOCKHOLDERS’ EQUITY:
Common stock	29	29
Additional paid-in capital	175,352	198,384
Accumulated other comprehensive loss	(2,382)	(2,139)
Retained earnings	360,833	351,408
Total stockholders’ equity	533,832	547,682
Total liabilities and stockholders’ equity	$ 604,434	$ 621,074