Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Operating activities
Net income	$ 37,506	$ 33,335
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	13,539	12,831
Share-based Compensation	6,159	5,260
Deferred taxes	715	495
Loss on impairment of assets		455
Amortization of held-to-maturity securities	851	881
Other	21	(1,381)
Changes in operating assets and liabilities:
Accounts receivable	(10,679)	(1,626)
Inventories	(188)	(203)
Prepaid expenses and other	(1,147)	(1,107)
Income taxes	4,158	8,114
Accounts payable	1,387	(2,043)
Accrued liabilities and other	6,678	3,131
Net cash provided by operating activities	59,000	58,142
Investing activities
Purchases of property and equipment	(24,164)	(30,981)
Purchases of marketable securities	(20,037)	(56,213)
Proceeds from maturities of marketable securities	34,090	45,907
Purchases of other investments	(514)
Net cash used in investing activities	(10,625)	(41,287)
Financing activities
Acquisition-related contingent consideration		(400)
Proceeds from exercises of stock options and other	5,749	4,168
Repurchases of common stock	(4,410)
Net cash provided by financing activities	1,339	3,768
Effect of exchange rate changes on cash and cash equivalents	774	(58)
Net increase in cash and cash equivalents	50,488	20,565
Cash and cash equivalents, beginning of period	68,795	47,653
Cash and cash equivalents, end of period	$ 119,283	$ 68,218