Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Cash flows from operating activities:
Net income	$ 100,582	$ 65,922
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	12,649	8,829
Amortization of premium on available-for-sale securities	1,926	1,121
(Gain) loss on deferred compensation plan investments	(3,039)	178
Deferred taxes, net	1,005	3,400
Stock-based compensation expense	60,710	39,606
Other	5	3
Changes in operating assets and liabilities:
Accounts receivable	(10,719)	(2,428)
Inventories	(20,237)	(24,580)
Other assets	(4,109)	(10,001)
Accounts payable	12,791	15,489
Accrued compensation and related benefits	9,398	6,773
Income tax liabilities	1,640	(61)
Other accrued liabilities	11,401	6,498
Net cash provided by operating activities	174,003	110,749
Cash flows from investing activities:
Purchases of property and equipment	(58,268)	(24,535)
Purchases of short-term investments	(255,343)	(189,637)
Proceeds from maturities and sales of short-term investments	62,789	118,701
Proceeds from sales of long-term investments	300	125
Contributions to deferred compensation plan, net	(1,686)	(775)
Net cash used in investing activities	(252,208)	(96,121)
Cash flows from financing activities:
Property and equipment purchased on extended payment terms	(1,140)	(4,061)
Proceeds from common stock issued under the employee equity incentive plan	12,920	14,110
Proceeds from common stock issued under the employee stock purchase plan	2,293	1,892
Dividends and dividend equivalents paid	(52,222)	(42,267)
Net cash used in financing activities	(38,149)	(30,326)
Effect of change in exchange rates	1,615	(777)
Net decrease in cash, cash equivalents and restricted cash	(114,739)	(16,475)
Cash, cash equivalents and restricted cash, beginning of period	335,071	173,076
Cash, cash equivalents and restricted cash, end of period	220,332	156,601
Supplemental disclosures for cash flow information:
Cash paid for taxes	9,023	633
Non-cash investing and financing activities:
Liability accrued for property and equipment purchases	10,719	7,258
Liability accrued for dividends and dividend equivalents	$ 30,564	$ 25,044