Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash flows from operating activities:
Net income	$ 53,132	$ 36,146
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of intangible assets	12,092	10,542
Loss on sales or write-off of property and equipment		58
Amortization of premium on available-for-sale investments	1,494	619
Gain on deferred compensation plan investments	(1,902)	(1,097)
Deferred taxes, net		12
Excess tax benefits from equity awards		(1,078)
Stock-based compensation expense	40,759	34,241
Changes in operating assets and liabilities:
Accounts receivable	(16,505)	(2,503)
Inventories	(28,384)	(7,522)
Other assets	1,696	(10,869)
Accounts payable	4,999	5,713
Accrued compensation and related benefits	4,542	6,549
Accrued liabilities	7,276	4,308
Income tax liabilities	1,249	1,668
Net cash provided by operating activities	80,448	76,787
Cash flows from investing activities:
Property and equipment purchases	(25,108)	(29,036)
Purchases of short-term investments	(102,274)	(147,055)
Proceeds from maturities and sales of short-term investments	61,678	140,733
Contributions to deferred compensation plan, net	(2,124)	(2,314)
Net cash used in investing activities	(67,828)	(37,672)
Cash flows from financing activities:
Property and equipment purchased on extended payment terms	(250)	(150)
Proceeds from exercise of stock options	129	1,191
Proceeds from shares issued under the employee stock purchase plan	2,701	2,463
Dividends and dividend equivalents paid	(25,264)	(24,634)
Excess tax benefits from equity awards		1,078
Net cash used in financing activities	(22,684)	(20,052)
Effect of change in exchange rates	1,785	(444)
Net increase (decrease) in cash and cash equivalents	(8,279)	18,619
Cash and cash equivalents, beginning of period	112,703	90,860
Cash and cash equivalents, end of period	104,424	109,479
Supplemental disclosures for cash flow information:
Cash paid for taxes and interest	1,855	843
Supplemental disclosures of non-cash investing and financing activities:
Liability accrued for property and equipment purchases	284	197
Liability accrued for dividends and dividend equivalents	$ 10,131	$ 9,882