Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Operating activities:
Consolidated net income	$ 4,990	$ 15,095
Adjustments to reconcile consolidated net income to net cash provided by (used for) operating activities:
Depreciation and amortization	3,296	2,806
Stock-based compensation expense	1,994	1,571
Decrease in long-term deferred revenue	(81)	(80)
Decrease (increase) in other assets	62	(26)
Increase in long-term income taxes payable	5	5
Deferred income taxes	2	2
Credit gain on available-for-sale securities	(1)	(1)
Change in current assets and liabilities, net	(5,682)	(1,599)
Net cash provided by operating activities	4,585	17,773
Investing activities:
Purchases of short-term investments	0	(50,706)
Sales or maturities of short-term investments	25,000	5,000
Additions to property, plant and equipment	(22,683)	(9,264)
Net cash provided by (used for) investing activities	2,317	(54,970)
Financing activities:
Proceeds from employee stock plans	1,810	3,050
Payment of contingent consideration obligations	0	(46)
Net cash provided by financing activities	1,810	3,004
Effect of foreign exchange rates on cash	(80)	(138)
Net increase (decrease) in cash and cash equivalents	8,632	(34,331)
Cash and cash equivalents at beginning of period	182,418	161,742
Cash and cash equivalents at end of period	$ 191,050	$ 127,411