Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities:
Net income	$ 46,874	$ 46,062
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	6,994	5,830
Loss on sales of property and equipment	15	0
Amortization of premium on available-for-sale securities	216	808
Gain on deferred compensation plan investments	(2,555)	(233)
Deferred taxes, net	(20)	12
Stock-based compensation expense	38,719	30,921
Changes in operating assets and liabilities:
Accounts receivable	(176)	(16,325)
Inventories	(7,205)	(29,602)
Other assets	(42)	(983)
Accounts payable	2,153	3,032
Accrued compensation and related benefits	4,124	103
Accrued liabilities	423	539
Income tax liabilities	(6,627)	1,546
Net cash provided by operating activities	82,893	41,710
Cash flows from investing activities:
Purchases of property and equipment	(77,638)	(12,998)
Acquisition of in-place leases	(981)	0
Purchases of short-term investments	(21,546)	(67,002)
Proceeds from maturities and sales of short-term investments	57,999	51,059
Proceeds from sales of long-term investments	75	0
Proceeds from sales of property and equipment	1,456	0
Contributions to deferred compensation plan, net	(1,435)	(911)
Net cash used in investing activities	(42,070)	(29,852)
Cash flows from financing activities:
Property and equipment purchased on extended payment terms	(3)	0
Proceeds from exercise of stock options	0	59
Proceeds from vesting of restricted stock units	12,471	8,709
Proceeds from shares issued under the employee stock purchase plan	1,627	1,562
Dividends and dividend equivalents paid	(30,784)	(21,467)
Net cash used in financing activities	(16,689)	(11,137)
Effect of change in exchange rates	175	(407)
Net increase in cash, cash equivalents and restricted cash	24,309	314
Cash, cash equivalents and restricted cash, beginning of period	172,818	82,874
Cash, cash equivalents and restricted cash, end of period	197,127	83,188
Supplemental disclosures for cash flow information:
Cash paid for taxes	7,168	3,884
Non-cash investing and financing activities:
Liability accrued for property and equipment purchases	3,028	2,939
Liability accrued for dividends and dividend equivalents	$ 19,749	$ 14,530