Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net income	$ 164,375	$ 108,839	$ 105,268
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	19,186	14,867	12,311
Amortization of premium on available-for-sale securities	2,979	729	1,353
(Gain) loss on deferred compensation plan investments	(4,592)	(3,806)	255
Deferred taxes, net	(1,627)	(577)	(843)
Stock-based compensation expense	85,551	78,699	60,607
Other	(1,072)	(259)	22
Changes in operating assets and liabilities:
Accounts receivable	(14,123)	2,512	(18,079)
Inventories	(29,503)	8,865	(37,060)
Other assets	(3,003)	(10,204)	(1,075)
Accounts payable	10,410	3,048	871
Accrued compensation and related benefits	18,524	7,496	3,806
Income tax liabilities	747	(1,355)	6,923
Other accrued liabilities	19,951	7,449	7,092
Net cash provided by operating activities	267,803	216,303	141,451
Cash flows from investing activities:
Purchases of property and equipment	(55,639)	(95,806)	(22,526)
Proceeds from sales of property and equipment	29	9,268	0
Acquisition of in-place leases	0	(981)	0
Purchases of short-term investments	(334,947)	(212,562)	(99,199)
Proceeds from maturities and sales of short-term investments	357,092	135,801	109,131
Purchases of long-term investments	(3,316)	0	0
Proceeds from sales of long-term investments	300	250	2,000
Contributions to deferred compensation plan, net	(2,696)	(3,082)	(4,146)
Net cash used in investing activities	(39,177)	(167,112)	(14,740)
Cash flows from financing activities:
Property and equipment purchased on extended payment terms	(5,357)	(683)	(749)
Proceeds from common stock issued under the employee equity incentive plan	18,767	16,650	10,637
Proceeds from common stock issued under the employee stock purchase plan	3,819	3,277	3,028
Dividends and dividend equivalents paid	(88,786)	(67,294)	(47,475)
Net cash used in financing activities	(71,557)	(48,050)	(34,559)
Effect of change in exchange rates	4,926	(883)	(2,208)
Net increase in cash, cash equivalents and restricted cash	161,995	258	89,944
Cash, cash equivalents and restricted cash, beginning of period	173,076	172,818	82,874
Cash, cash equivalents and restricted cash, end of period	335,071	173,076	172,818
Supplemental disclosures for cash flow information:
Cash paid for taxes	1,405	10,700	7,134
Non-cash investing and financing activities:
Liability accrued for property and equipment purchases	7,839	7,803	1,737
Liability accrued for dividends and dividend equivalents	$ 27,507	$ 21,955	$ 16,319