Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities:
Net income	$ 26,181	$ 21,856
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	3,255	2,755
Loss on sales of property and equipment	14
Amortization of premium on available-for-sale securities	121	435
(Gain) loss on deferred compensation plan investments	(1,935)	66
Deferred taxes, net	(33)
Stock-based compensation expense	16,010	15,030
Changes in operating assets and liabilities:
Accounts receivable	(3,676)	(11,103)
Inventories	(6,171)	(12,590)
Other assets	(1,576)	(3,954)
Accounts payable	4,778	3,856
Accrued compensation and related benefits	4	(2,821)
Accrued liabilities	3,355	4,998
Income tax liabilities	(1,491)	(2,236)
Net cash provided by operating activities	38,836	16,292
Cash flows from investing activities:
Purchases of property and equipment	(58,376)	(7,400)
Acquisition of in-place leases	(981)
Purchases of short-term investments		(47,565)
Proceeds from maturities and sales of short-term investments	28,076	31,063
Proceeds from sales of property and equipment	1,456
Contributions to deferred compensation plan, net	(956)	(1,300)
Net cash used in investing activities	(30,781)	(25,202)
Cash flows from financing activities:
Property and equipment purchased on extended payment terms	(10)
Proceeds from exercise of stock options		16
Proceeds from vesting of restricted stock units	10,383	7,793
Proceeds from shares issued under the employee stock purchase plan	1,627	1,563
Dividends and dividend equivalents paid	(12,761)	(8,339)
Net cash provided by (used in) financing activities	(761)	1,033
Effect of change in exchange rates	1,770	1,137
Net increase (decrease) in cash, cash equivalents and restricted cash	9,064	(6,740)
Cash, cash equivalents and restricted cash, beginning of period	172,818	82,874
Cash, cash equivalents and restricted cash, end of period	181,882	76,134
Supplemental disclosures for cash flow information:
Cash paid for taxes and interest	393	3,374
Non-cash investing and financing activities:
Liability accrued for property and equipment purchases	958	2,491
Liability accrued for dividends and dividend equivalents	$ 18,534	$ 13,603