Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Operating activities
Net income	$ 15,511	$ 18,051
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	7,439	6,259
Stock-based compensation expense	3,040	2,307
Deferred taxes	379	612
Amortization of held-to-maturity securities	16	163
Other	236	106
Changes in operating assets and liabilities:
Accounts receivable	(2,386)	(4,013)
Inventories	739	807
Prepaid expenses and other	(211)	(1,707)
Income taxes	3,006	2,387
Accounts payable	(805)	2,291
Accrued liabilities and other	(8,962)	(1,118)
Net cash provided by operating activities	18,002	26,145
Investing activities
Purchases of property, equipment and other capital assets	(12,735)	(25,513)
Cash used for acquisitions, net of cash acquired		(90)
Purchases of other assets and investments	(4,000)
Purchases of marketable securities		(3,389)
Proceeds from maturities of marketable securities	17,006	13,551
Net cash provided by (used in) investing activities	271	(15,441)
Financing activities
Payments on debt		(5,000)
Proceeds from exercises of stock options	174	2,880
Purchases of shares withheld for tax obligations	(594)	(628)
Repurchases of common stock	(17,309)
Net cash used in financing activities	(17,729)	(2,748)
Effect of exchange rate changes on cash and cash equivalents	(240)	432
Net increase in cash and cash equivalents	304	8,388
Cash and cash equivalents, beginning of period	85,046	36,707
Cash and cash equivalents, end of period	$ 85,350	$ 45,095