CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 29,078	$ 18,078
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	11,069	9,431
Amortization of intangibles	2,207	2,483
Loss on disposal of property and equipment	292	152
Stock-based compensation expense	12,691	9,903
Amortization of premium (accretion of discount) on marketable securities	321	(230)
Deferred income taxes	1,279	1,659
Increase (decrease) in accounts receivable allowance for credit losses	(154)	57
Change in operating assets and liabilities:
Accounts receivable	11,556	(14,453)
Inventories	(13,583)	(8,340)
Prepaid expenses and other assets	4,092	(3,614)
Accounts payable	5,861	4,153
Taxes payable and accrued liabilities	(1,665)	1,217
Net cash provided by operating activities	63,044	20,496
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(21,622)	(8,348)
Proceeds from sale of property and equipment	331	0
Acquisition of technology licenses	0	(251)
Purchases of marketable securities	(19,827)	(54,424)
Proceeds from sales and maturities of marketable securities	58,962	19,422
Net cash provided by (used in) investing activities	17,844	(43,601)
CASH FLOWS FROM FINANCING ACTIVITIES:
Issuance of common stock under employee stock plans	6,298	5,678
Repurchase of common stock	(2,636)	(7,302)
Payments of dividends to stockholders	(11,915)	(9,917)
Net cash used in financing activities	(8,253)	(11,541)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	72,635	(34,646)
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	178,690	134,137
CASH AND CASH EQUIVALENTS AT END OF PERIOD	251,325	99,491
SUPPLEMENTAL DISCLOSURE OF NON-CASH INVESTING AND FINANCING ACTIVITIES:
Unpaid property and equipment	13,932	2,098
Unpaid technology licenses	0	100
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION:
Cash paid (received) for income taxes, net	$ (2,155)	$ 890