Consolidated Statements of Cash Flows $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Cash flows from operating activities:
Net income	$ 35,172	$ 35,495	$ 22,898
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of intangible assets	13,783	13,130	12,160
Loss (gain) on sales of property and equipment	(339)		31
Premium amortization and loss on investments	596	96	443
Change in fair value of contingent consideration	(2,507)
Deferred taxes, net	42	17	(81)
Stock-based compensation expense	41,563	33,454	20,701
Excess tax benefit from equity awards	(5,928)	(10)
Changes in operating assets and liabilities, net of effects of an acquisition:
Accounts receivable	(5,201)	(1,870)	(4,347)
Inventories	(22,210)	(1,142)	(7,606)
Prepaid expenses and other assets	(390)	(2,029)	121
Accounts payable	147	1,632	1,440
Accrued liabilities	9,942	(3,102)	12,149
Income tax liabilities	3,998	(248)	86
Accrued compensation and related benefits	1,068	(1,290)	2,691
Net cash provided by operating activities	69,736	74,133	60,686
Cash flows from investing activities:
Property and equipment purchases	(16,024)	(9,511)	(15,764)
Proceeds from sales of property and equipment	340		88
Purchases of short-term investments	(223,018)	(136,872)	(125,756)
Proceeds from sales of short-term investments	189,549	149,291	85,700
Proceeds from sales of long-term investments		4,650	2,025
Contributions to employee deferred compensation plan, net	(8,044)	(5,335)	(617)
Cash paid for an acquisition, net of cash acquired		(11,590)
Net cash used in investing activities	(57,197)	(9,367)	(54,324)
Cash flows from financing activities:
Property and equipment purchased on extended payment terms	(300)	(400)	(557)
Proceeds from exercise of stock options	7,744	11,941	37,877
Proceeds from shares issued under the employee stock purchase plan	2,227	2,078	2,145
Repurchases of common shares	(32,286)	(41,198)	(20,615)
Dividends and dividend equivalents paid	(29,965)	(11,658)
Excess tax benefit from equity awards	5,928	10
Net cash provided by (used in) financing activities	(46,652)	(39,227)	18,850
Effect of change in exchange rates	(1,293)	(486)	897
Net increase (decrease) in cash and cash equivalents	(35,406)	25,053	26,109
Cash and cash equivalents, beginning of period	126,266	101,213	75,104
Cash and cash equivalents, end of period	90,860	126,266	101,213
Supplemental disclosures for cash flow information:
Cash paid for taxes and interest	3,322	1,235	1,116
Supplemental disclosures of non-cash investing and financing activities:
Liability accrued for property and equipment purchases	2,184	1,487	$ 1,941
Liability accrued for dividends and dividend equivalents	$ 10,109	6,660
Sensima [Member]
Supplemental disclosures of non-cash investing and financing activities:
Fair value of contingent consideration related to an acquisition		$ 2,507