CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 43,898	$ 35,177
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	17,071	14,262
Amortization of intangibles	3,283	3,840
Loss on disposal of property and equipment	311	214
Stock-based compensation expense	22,049	15,009
Amortization of premium (accretion of discount) on marketable securities	525	(296)
Deferred income taxes	100	1,278
Increase in accounts receivable allowance for credit losses, net	155	57
Change in operating assets and liabilities:
Accounts receivable	(5,328)	(14,804)
Inventories	(14,425)	(7,853)
Prepaid expenses and other assets	6,133	(3,034)
Accounts payable	6,365	(2,636)
Taxes payable and accrued liabilities	(864)	1,126
Net cash provided by operating activities	79,273	42,340
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(35,738)	(14,325)
Proceeds from sale of property and equipment	331	0
Acquisition of technology licenses	0	(351)
Purchases of marketable securities	(66,066)	(135,288)
Proceeds from sales and maturities of marketable securities	86,995	66,184
Net cash used in investing activities	(14,478)	(83,780)
CASH FLOWS FROM FINANCING ACTIVITIES:
Issuance of common stock under employee stock plans	9,662	9,683
Repurchase of common stock	(2,636)	(7,302)
Payments of dividends to stockholders	(18,497)	(14,916)
Net cash used in financing activities	(11,471)	(12,535)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	53,324	(53,975)
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	178,690	134,137
CASH AND CASH EQUIVALENTS AT END OF PERIOD	232,014	80,162
SUPPLEMENTAL DISCLOSURE OF NON-CASH INVESTING AND FINANCING ACTIVITIES:
Unpaid property and equipment	14,180	2,868
Unpaid technology licenses	0	675
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION:
Cash paid (received) for income taxes, net	$ (1,927)	$ 1,083