Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Operating activities
Net income	$ 31,677	$ 36,365
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	14,981	12,749
Stock-based compensation expense	6,526	5,034
Deferred taxes	1,585	1,620
Gain on sale of businesses	0	(671)
Amortization of held-to-maturity securities	7	276
Other	(279)	7
Changes in operating assets and liabilities:
Accounts receivable	(3,461)	(2,648)
Inventories	392	389
Prepaid expenses and other	24	(1,059)
Income taxes	4,833	133
Accounts payable	3,848	4,408
Accrued liabilities and other	(5,245)	2,714
Net cash provided by operating activities	54,888	59,317
Investing activities
Purchases of property, equipment and other capital assets	(34,136)	(43,194)
Cash used for acquisitions, net of cash acquired	0	(90)
Proceeds from sale of business	0	284
Purchases of other assets and investments	(4,000)	0
Purchases of marketable securities	(8,983)	(17,129)
Proceeds from maturities of marketable securities	29,170	29,056
Net cash used in investing activities	(17,949)	(31,073)
Financing activities
Payments on debt	0	(5,000)
Proceeds from exercises of stock options	2,243	4,696
Purchases of shares withheld for tax obligations	(2,418)	(1,390)
Repurchases of common stock	(21,410)	0
Net cash used in financing activities	(21,585)	(1,694)
Effect of exchange rate changes on cash and cash equivalents	135	(652)
Net increase in cash and cash equivalents	15,489	25,898
Cash and cash equivalents, beginning of period	85,046	36,707
Cash and cash equivalents, end of period	$ 100,535	$ 62,605