Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash flows from operating activities:
Net income	$ 46,062	$ 29,490
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of intangible assets	5,830	8,063
Amortization of premium on available-for-sale investments	808	1,005
Gain on deferred compensation plan investments	(233)	(1,266)
Stock-based compensation expense	30,921	26,789
Deferred taxes, net	12
Changes in operating assets and liabilities:
Accounts receivable	(16,325)	(7,729)
Inventories	(29,602)	(21,158)
Other assets	(983)	(1,167)
Accounts payable	3,032	7,755
Accrued compensation and related benefits	103	1,733
Accrued liabilities	539	3,177
Income tax liabilities	1,546	78
Net cash provided by operating activities	41,710	46,770
Cash flows from investing activities:
Property and equipment purchases	(12,998)	(20,528)
Purchases of short-term investments	(67,002)	(93,398)
Proceeds from maturities and sales of short-term investments	51,059	41,809
Contributions to deferred compensation plan, net	(911)	(1,594)
Net cash used in investing activities	(29,852)	(73,711)
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	8,709
Proceeds from shares issued under the employee stock purchase plan	1,562	1,382
Dividends and dividend equivalents paid	(21,467)	(16,815)
Net cash used in financing activities	(11,137)	(15,554)
Effect of change in exchange rates	(407)	909
Net increase (decrease) in cash, cash equivalents and restricted cash	314	(41,586)
Cash, cash equivalents and restricted cash, beginning of period	82,874	112,813
Cash, cash equivalents and restricted cash, end of period	83,188	71,227
Supplemental disclosures:
Cash paid for taxes and interest	3,884	1,583
Non-cash investing and financing activities:
Liability accrued for property and equipment purchases	2,939	974
Liability accrued for dividends and dividend equivalents	$ 14,530	$ 9,536