Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Cash flows from operating activities:
Net income	$ 10,575	$ 5,963
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of intangible assets	3,320	$ 3,621
Loss on sales of property and equipment	58
Gains on investments, net	(131)	$ (105)
Deferred taxes, net	11
Stock-based compensation expense	8,979	$ 9,219
Changes in operating assets and liabilities:
Accounts receivable	1,998	286
Inventories	851	(12,467)
Prepaid expenses and other assets	(181)	362
Accounts payable	3,342	6,902
Accrued liabilities	344	3,339
Income tax liabilities	(26)	187
Accrued compensation and related benefits	(270)	(1,626)
Net cash provided by operating activities	28,870	15,681
Cash flows from investing activities:
Property and equipment purchases	(5,346)	(4,703)
Purchases of short-term investments	(66,803)	(59,617)
Proceeds from sales of short-term investments	37,353	34,389
Contributions to employee deferred compensation plan, net	(1,030)	(2,176)
Net cash used in investing activities	(35,826)	(32,107)
Cash flows from financing activities:
Proceeds from Stock Options Exercised	464	1,292
Proceeds from Stock Plans	$ 1,285	1,121
Repurchases of common shares		(10,405)
Dividends and dividend equivalents paid	$ (7,974)	(5,859)
Net cash used in financing activities	(6,225)	(13,851)
Effect of change in exchange rates	129	(23)
Net decrease in cash and cash equivalents	(13,052)	(30,300)
Cash and cash equivalents, beginning of period	90,860	126,266
Cash and cash equivalents, end of period	77,808	95,966
Supplemental disclosures for cash flow information:
Cash paid for taxes and interest	349	242
Supplemental disclosures of non-cash investing and financing activities:
Liability accrued for property and equipment purchases	840	1,522
Liability accrued for dividends and dividend equivalents	$ 8,700	$ 8,459