CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
OPERATING ACTIVITIES:
Net income (loss)	$ 629,000	$ (62,147,000)	$ 4,930,000
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation and amortization	14,239,000	18,516,000	18,313,000
Compensation for stock options and restricted stock units	8,314,000	11,071,000	7,620,000
Provision for bad debts (net of recoveries)	440,000	2,090,000	907,000
Loss on disposal of assets	383,000	2,639,000	192,000
Provision for excess and obsolete inventory	1,349,000	16,886,000	5,757,000
Impairment of goodwill	0	21,233,000	0
Impairment of acquired intangibles	0	10,548,000	0
Impairment of loan to affiliate	0	549,000	0
Deferred income tax (benefit) expense	(28,444,000)	(6,304,000)	689,000
(Increase) decrease in:
Accounts receivable, net	12,346,000	10,406,000	(15,995,000)
Inventories	10,343,000	(4,136,000)	(20,532,000)
Prepaid expenses and other assets	3,862,000	1,188,000	(11,310,000)
Increase (decrease) in:
Accounts payable and accrued liabilities	2,390,000	(2,518,000)	11,195,000
Income taxes payable	(3,357,000)	1,041,000	(3,286,000)
Net cash provided by operating activities	21,394,000	32,468,000	6,323,000
INVESTING ACTIVITIES:
Purchases of investments	0	(50,000,000)	(47,000,000)
Proceeds from sale of investments	25,000,000	50,000,000	33,000,000
Purchases of property and equipment	(4,774,000)	(6,675,000)	(11,021,000)
Payments for internally capitalized patents	(1,298,000)	(2,118,000)	(1,900,000)
Acquisition of business, net of cash received	(6,036,000)	0	(27,067,000)
Other	1,015,000	(549,000)	(1,786,000)
Net cash provided (used in) by investing activities	13,907,000	(9,342,000)	(55,774,000)
FINANCING ACTIVITIES:
Payments on capital leases	(338,000)	(358,000)	(157,000)
Payments of contingent consideration for acquisitions	(733,000)	(3,101,000)	(888,000)
Payments for taxes related to net share settlement of equity awards	(2,602,000)	(2,199,000)	0
Proceeds from issuance of stock related to stock option exercises	14,731,000	7,901,000	20,855,000
Net cash provided by financing activities	11,058,000	2,243,000	19,810,000
EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS	5,640,000	(518,000)	(2,536,000)
INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	51,999,000	24,851,000	(32,177,000)
CASH AND CASH EQUIVALENTS, BEGINNING OF YEAR	133,634,000	108,783,000	140,960,000
CASH AND CASH EQUIVALENTS, END OF YEAR	185,633,000	133,634,000	108,783,000
Customer deposits
Increase (decrease) in:
Increase (decrease) in contract with customer, liability	(374,000)	(30,000)	513,000
Unearned service revenues
Increase (decrease) in:
Increase (decrease) in contract with customer, liability	$ (726,000)	$ 11,436,000	$ 7,330,000