CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 27,609	$ 48,898	$ 39,152
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	18,374	16,812	16,464
Amortization of intangibles	6,083	6,663	7,039
Loss on disposal of property and equipment	360	332	361
Stock-based compensation expense	24,677	20,885	14,767
Amortization of premium on marketable securities	1,100	555	1,063
Deferred income taxes	15,838	(638)	(5,508)
Increase in accounts receivable allowances	209	207	127
Tax shortfall associated with employee stock plans	0	0	(189)
Change in operating assets and liabilities:
Accounts receivable	(10,479)	751	4,144
Inventories	(4,523)	(630)	13,500
Prepaid expenses and other assets	(17,646)	(2,524)	3,342
Accounts payable	396	7,714	(2,000)
Taxes payable and accrued liabilities	20,041	(1,124)	(75)
Net cash provided by operating activities	82,039	97,901	92,187
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(32,496)	(12,198)	(11,359)
Payment for purchase of building (Note 14)	0	0	(10,389)
Payment for acquisition, net of cash acquired (Note 14)	0	0	(15,549)
Purchases of marketable securities	(151,663)	(188,654)	(29,748)
Proceeds from sales and maturities of marketable securities	149,443	83,423	59,309
Net cash used in investing activities	(34,716)	(117,429)	(7,736)
CASH FLOWS FROM FINANCING ACTIVITIES:
Issuance of common stock under employee stock plans	10,020	13,059	12,580
Repurchase of common stock	(9,188)	(6,435)	(53,731)
Payments of dividends to stockholders	(16,634)	(15,054)	(13,916)
Proceeds from draw on line of credit	5,000	0	0
Payments on line of credit	(5,000)	0	0
Net cash used in financing activities	(15,802)	(8,430)	(55,067)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	31,521	(27,958)	29,384
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	62,134	90,092	60,708
CASH AND CASH EQUIVALENTS AT END OF PERIOD	93,655	62,134	90,092
SUPPLEMENTAL DISCLOSURE OF NON-CASH INVESTING AND FINANCING ACTIVITIES:
Unpaid property and equipment	4,913	1,825	1,472
Loan applied to CamSemi purchase price (Note 14)	0	0	6,600
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION:
Cash paid (refund) for income taxes, net of refunds (Note 11)	$ (1,571)	$ 6,613	$ 473