Condensed Consolidated Statements of Cash Flows (Unudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Cash flows from operating activities:
Net income	$ 29,490	$ 21,773
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of intangible assets	8,063	6,873
Loss on sales or write-off of property and equipment		58
Amortization of premium on available-for-sale investments	1,005	363
Gain on deferred compensation plan investments	(1,266)	(607)
Deferred taxes, net		12
Excess tax benefits from equity awards		(361)
Stock-based compensation expense	26,789	20,726
Changes in operating assets and liabilities:
Accounts receivable	(7,729)	(520)
Inventories	(21,158)	(6,758)
Other assets	(1,167)	(10,417)
Accounts payable	7,755	7,176
Accrued compensation and related benefits	1,733	4,386
Accrued liabilities	3,177	769
Income tax liabilities	78	395
Net cash provided by operating activities	46,770	43,868
Cash flows from investing activities:
Property and equipment purchases	(20,528)	(18,678)
Purchases of short-term investments	(93,398)	(106,004)
Proceeds from maturities and sales of short-term investments	41,809	87,919
Contributions to deferred compensation plan, net	(1,594)	(1,623)
Net cash used in investing activities	(73,711)	(38,386)
Cash flows from financing activities:
Property and equipment purchased on extended payment terms	(250)	(150)
Proceeds from exercise of stock options	129	1,040
Proceeds from shares issued under the employee stock purchase plan	1,382	1,285
Dividends and dividend equivalents paid	(16,815)	(16,480)
Excess tax benefits from equity awards		361
Net cash used in financing activities	(15,554)	(13,944)
Effect of change in exchange rates	902	(352)
Net decrease in cash and cash equivalents	(41,593)	(8,814)
Cash and cash equivalents, beginning of period	112,703	90,860
Cash and cash equivalents, end of period	71,110	82,046
Supplemental disclosures for cash flow information:
Cash paid for taxes and interest	1,583	712
Supplemental disclosures of non-cash investing and financing activities:
Liability accrued for property and equipment purchases	974	472
Liability accrued for dividends and dividend equivalents	$ 9,536	$ 9,312