Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net income	$ 77,630	$ 53,132
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of intangible assets	9,058	12,092
Amortization of premium on available-for-sale securities	1,122	1,494
Gain on deferred compensation plan investments	(949)	(1,902)
Stock-based compensation expense	45,765	40,759
Deferred taxes, net	3,169
Changes in operating assets and liabilities:
Accounts receivable	(22,752)	(16,505)
Inventories	(37,496)	(28,384)
Other assets	(665)	1,696
Accounts payable	5,978	4,999
Accrued compensation and related benefits	7,838	4,542
Accrued liabilities	4,635	7,276
Income tax liabilities	528	1,249
Net cash provided by operating activities	93,861	80,448
Cash flows from investing activities:
Property and equipment purchases	(18,057)	(25,108)
Purchases of short-term investments	(86,021)	(102,274)
Proceeds from maturities and sales of short-term investments	83,679	61,678
Contributions to deferred compensation plan, net	(1,396)	(2,124)
Net cash used in investing activities	(21,795)	(67,828)
Cash flows from financing activities:
Property and equipment purchased on extended payment terms		(250)
Proceeds from exercise of stock options	59	129
Proceeds from vesting of restricted stock units	9,625
Proceeds from shares issued under the employee stock purchase plan	3,028	2,701
Dividends and dividend equivalents paid	(34,381)	(25,264)
Net cash used in financing activities	(21,669)	(22,684)
Effect of change in exchange rates	(2,062)	1,790
Net increase (decrease) in cash, cash equivalents and restricted cash	48,335	(8,274)
Cash, cash equivalents and restricted cash, beginning of period	82,874	112,813
Cash, cash equivalents and restricted cash, end of period	131,209	104,539
Supplemental disclosures:
Cash paid for taxes and interest	6,388	1,855
Non-cash investing and financing activities:
Liability accrued for property and equipment purchases	1,563	284
Liability accrued for dividends and dividend equivalents	$ 15,397	$ 10,131