Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities:
Net income	$ 45,413	$ 35,756
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	5,529	4,328
Amortization of premium on available-for-sale securities	813	494
(Gain) loss on deferred compensation plan investments	(1,177)	3,750
Deferred taxes, net	1,004	3,412
Stock-based compensation expense	28,583	18,562
Other	5	(1)
Changes in operating assets and liabilities:
Accounts receivable	(17,236)	(1,635)
Inventories	(18,151)	(3,994)
Other assets	(2,215)	(10,061)
Accounts payable	13,513	7,185
Accrued compensation and related benefits	10,609	(7,374)
Income tax liabilities	1,800	34
Other accrued liabilities	8,567	963
Net cash provided by operating activities	77,057	51,419
Cash flows from investing activities:
Purchases of property and equipment	(18,970)	(9,951)
Purchases of short-term investments	(201,517)	(101,566)
Proceeds from maturities and sales of short-term investments	38,472	47,397
Proceeds from sales of long-term investments	25	100
Contributions to deferred compensation plan, net	(876)	(438)
Net cash used in investing activities	(182,866)	(64,458)
Cash flows from financing activities:
Property and equipment purchased on extended payment terms	(563)	(279)
Proceeds from common stock issued under the employee equity incentive plan	10,744	11,758
Proceeds from common stock issued under the employee stock purchase plan	2,293	1,892
Dividends and dividend equivalents paid	(23,467)	(17,427)
Net cash used in financing activities	(10,993)	(4,056)
Effect of change in exchange rates	218	(985)
Net decrease in cash, cash equivalents and restricted cash	(116,584)	(18,080)
Cash, cash equivalents and restricted cash, beginning of period	335,071	173,076
Cash, cash equivalents and restricted cash, end of period	218,487	154,996
Supplemental disclosures for cash flow information:
Cash paid for taxes	377	279
Non-cash investing and financing activities:
Liability accrued for property and equipment purchases	12,963	10,909
Liability accrued for dividends and dividend equivalents	$ 29,000	$ 23,725