Condensed Consolidated Statements of Cash Flows (Unudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Cash flows from operating activities:
Net income	$ 14,477	$ 10,575
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of intangible assets	4,044	3,320
(Gain) loss on sales or write-off of property and equipment	(3)	58
Amortization of premium on available-for-sale investments, net	507	171
Gain on employee deferred compensation plan investments	(733)	(302)
Deferred taxes, net		11
Stock-based compensation expense	11,662	8,979
Changes in operating assets and liabilities:
Accounts receivable	(3,865)	1,998
Inventories	(7,057)	851
Other assets	(1,465)	(181)
Accounts payable	4,927	3,342
Accrued compensation and related benefits	(2,251)	(270)
Accrued liabilities	2,402	344
Income tax liabilities	(753)	(26)
Net cash provided by operating activities	21,892	28,870
Cash flows from investing activities:
Property and equipment purchases	(3,424)	(5,346)
Proceeds from sales of property and equipment	3
Purchases of short-term investments	(71,989)	(66,803)
Proceeds from maturities and sales of short-term investments	25,400	37,353
Contributions to employee deferred compensation plan, net	(1,233)	(1,030)
Net cash used in investing activities	(51,243)	(35,826)
Cash flows from financing activities:
Property and equipment purchased on extended payment terms	(250)
Proceeds from exercise of stock options	61	464
Proceeds from shares issued under the employee stock purchase plan	1,382	1,285
Dividends and dividend equivalents paid	(8,179)	(7,974)
Net cash used in financing activities	(6,986)	(6,225)
Effect of change in exchange rates	460	129
Net decrease in cash and cash equivalents	(35,877)	(13,052)
Cash and cash equivalents, beginning of period	112,703	90,860
Cash and cash equivalents, end of period	76,826	77,808
Supplemental disclosures for cash flow information:
Cash paid for taxes and interest	1,220	349
Supplemental disclosures of non-cash investing and financing activities:
Liability accrued for property and equipment purchases	1,208	840
Liability accrued for dividends and dividend equivalents	$ 8,902	$ 8,700