CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 55,735	$ 170,851	$ 164,413
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	35,203	34,930	31,454
Amortization of intangibles	2,173	2,415	3,494
Loss on disposal of property and equipment	100	1,371	3,105
Stock-based compensation expense	28,528	22,364	37,609
Amortization of premium (accretion of discount) on marketable securities	(351)	3,292	1,590
Deferred income taxes	(9,247)	(2,566)	(13,240)
Increase (decrease) in accounts receivable allowance for credit losses	(454)	690	18
Change in operating assets and liabilities:
Accounts receivable	6,616	19,867	(5,501)
Inventories	(27,744)	(36,154)	3,612
Prepaid expenses and other assets	(1,183)	7,343	4,326
Accounts payable	(5,435)	(3,836)	4,067
Taxes payable and accrued liabilities	(18,182)	(5,224)	(4,079)
Net cash provided by operating activities	65,759	215,343	230,868
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(20,884)	(39,211)	(47,272)
Proceeds from sale of property and equipment	0	1,202	35
Purchases of marketable securities	(191,211)	(55,820)	(554,018)
Proceeds from sales and maturities of marketable securities	197,942	172,165	368,457
Net cash provided by (used in) investing activities	(14,153)	78,336	(232,798)
CASH FLOWS FROM FINANCING ACTIVITIES:
Issuance of common stock under employee stock plans	6,237	6,162	7,710
Repurchase of common stock	(55,278)	(311,094)	(73,938)
Payments of dividends to stockholders	(44,008)	(41,492)	(32,599)
Net cash used in financing activities	(93,049)	(346,424)	(98,827)
NET DECREASE IN CASH AND CASH EQUIVALENTS	(41,443)	(52,745)	(100,757)
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	105,372	158,117	258,874
CASH AND CASH EQUIVALENTS AT END OF PERIOD	63,929	105,372	158,117
SUPPLEMENTAL DISCLOSURE OF NON-CASH INVESTING AND FINANCING ACTIVITIES:
Unpaid property and equipment	2,747	1,082	10,879
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION:
Cash paid for income taxes, net	$ 13,769	$ 17,880	$ 25,644