Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating activities
Net income	$ 63,655	$ 76,588	$ 51,778
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	30,864	26,754	18,474
Share-based Payment Arrangement, Noncash Expense, Total	10,781	10,928	8,558
Deferred taxes	6,106	11,936	1,174
Loss on impairment of assets	0	0	513
Gain on sale of businesses	0	(671)	0
Amortization of held-to-maturity securities	5	374	1,063
Other	391	(619)	(153)
Changes in operating assets and liabilities, net of acquisitions:
Accounts receivable	1,848	(6,098)	(9,933)
Inventories	60	(189)	(985)
Prepaid expenses and other	545	(2,098)	(691)
Income taxes	6,555	(6,652)	1,646
Accounts payable	(719)	1,942	3,176
Accrued liabilities and other	(4,039)	10,734	7,128
Net cash provided by operating activities	116,052	122,929	81,748
Investing activities
Purchases of property, equipment and other capital assets	(62,230)	(87,104)	(32,635)
Cash used for acquisitions, net of cash acquired	0	(90)	(110,533)
Proceeds from sale of businesses	0	284	0
Purchases of other assets and investments	(4,000)	(126)	(8,742)
Purchases of marketable securities	(46,403)	(41,384)	(20,037)
Proceeds from maturities of marketable securities	68,330	65,139	47,972
Net cash used in investing activities	(44,303)	(63,281)	(123,975)
Financing activities
Payments on debt	0	(5,000)	0
Proceeds from issuance of debt	0	0	5,000
Proceeds from exercises of stock options	4,391	8,935	8,602
Purchases of shares withheld for tax obligations	(2,487)	(2,144)	0
Repurchases of common stock	(33,521)	(12,229)	(4,410)
Net cash used in financing activities	(31,617)	(10,438)	9,192
Effect of exchange rate changes on cash and cash equivalents	47	(871)	947
Net increase (decrease) in cash and cash equivalents	40,179	48,339	(32,088)
Cash and cash equivalents, beginning of period	85,046	36,707	68,795
Cash and cash equivalents, end of period	125,225	85,046	36,707
Supplemental cash flow disclosure
Cash paid for interest	14	39	19
Cash paid for taxes	$ 4,002	$ 9,966	$ 19,113