Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Operating activities
Net income	$ 22,139	$ 21,058
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	6,940	4,683
Stock-based compensation expense	2,909	2,248
Deferred taxes	620	107
Excess tax benefit from stock-based compensation	(989)	(1,623)
Amortization of held-to-maturity securities	632	854
Changes in operating assets and liabilities:
Accounts receivable	(5,219)	(5,742)
Inventories	(663)	(306)
Prepaid expenses and other	(469)	(372)
Income taxes	(3,687)	2,431
Accounts payable	3,377	5,143
Accrued liabilities and other	2,243	(2,464)
Net cash provided by operating activities	27,833	26,017
Investing activities
Purchases of property and equipment	$ (15,717)	(31,625)
Acquisitions, net of cash acquired		(33,864)
Purchases of marketable securities	$ (25,389)	(38,463)
Proceeds from sales and maturities of marketable securities	24,109	55,441
Net cash used in investing activities	(16,997)	(48,511)
Financing activities
Payments on debt	(77)	(954)
Acquisition-related contingent consideration	(1,000)	(400)
Proceeds from exercises of stock options and other	2,207	1,806
Excess tax benefit from stock-based compensation	989	1,623
Net cash provided by financing activities	2,119	2,075
Effect of exchange rate changes on cash and cash equivalents	40	234
Net increase (decrease) in cash and cash equivalents	12,995	(20,185)
Cash and cash equivalents, beginning of period	43,329	43,039
Cash and cash equivalents, end of period	$ 56,324	$ 22,854