Unaudited Condensed Consolidated Statements of Cash Flows (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Cash Flows from Operating Activities:
Net income	$ 3,297,821	$ 3,803,818
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	1,418,759	1,666,510
Gain on write down / disposal of property and equipment, net	(28,960)
Loss on disposal of intangibles	95,500	73,226
Bond premium amortization		18,637
Recovery for doubtful accounts	(450)
Provision for excess and obsolete inventory	46,477	139,409
Provision (recovery) for warranty	168,768	(35,944)
Stock-based compensation expense	923,341	758,054
Litigation judgment recovery		(2,200,000)
Deferred income taxes	1,732,394	1,818,413
Provision for unrecognized tax benefits	57,500	12,368
Excess tax benefit from stock-based compensation	(1,909,761)
Change in assets and liabilities:
Accounts and notes receivable	1,294,722	(2,523,138)
Inventory	(893,658)	226,602
Prepaid and other assets	(1,133,644)	(524,842)
Accounts payable and accrued liabilities	(2,093,404)	100,483
Deferred revenue	1,659,052	225,409
Customer deposits	(114,873)	103,670
Net cash provided by operating activities	4,519,584	3,662,675
Cash Flows from Investing Activities:
Purchases of investments		(5,244,295)
Proceeds from call / maturity of investments	1,680,000	5,000,000
Purchases of property and equipment	(383,089)	(277,267)
Proceeds from disposal of fixed assets	33,709
Purchases of intangible assets	(103,513)	(122,541)
Net cash provided by (used in) investing activities	1,227,107	(644,103)
Cash Flows from Financing Activities:
Repurchase of common stock	(5,350,515)
Proceeds from options exercised	307,215	14,629
Payroll tax payments for net-settled stock awards	(178,070)
Excess tax benefit from stock-based compensation	1,909,761
Payments on capital lease obligation	(8,292)
Net cash (used in) provided by financing activities	(3,319,901)	14,629
Effect of exchange rate change on cash and cash equivalents	26,803	15,649
Net increase in cash and cash equivalents	2,453,593	3,048,850
Cash and cash equivalents, beginning of period	36,126,791	21,300,733
Cash and cash equivalents, end of period	38,580,384	24,349,583
Supplemental Disclosure:
Cash paid for income taxes - net	49,879	135,000
Non-Cash Transactions:
Property and equipment purchases in accounts payable	$ 226,752	$ 107,488