Condensed Consolidated Statements of Cash Flows (USD $)	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Cash Flows from Operating Activities:
Net income	$ 12,868,947	$ 10,922,936
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	4,036,337	5,113,989
(Gain) loss on write down / disposal of property and equipment, net	(29,160)	179,533
Loss on disposal of intangibles	112,980	125,605
Bond premium amortization	174,255	27,977
Provision (recovery) for doubtful accounts	1,711	(124,519)
Provision for excess and obsolete inventory	279,184	236,819
Provision for warranty	643,674	265,140
Stock-based compensation expense	2,905,635	2,197,050
Litigation judgment recovery		(2,200,000)
Deferred income taxes	5,211,841	2,886,003
Provision for unrecognized tax benefits	171,551	224,152
Excess tax benefit from stock-based compensation	(4,057,773)
Change in assets and liabilities:
Accounts and notes receivable	(1,993,766)	(2,646,621)
Inventory	(1,575,335)	817,110
Prepaids and other assets	(2,242,234)	(217,426)
Accounts payable and accrued liabilities	(496,274)	2,942,577
Deferred revenue	6,497,337	2,593,512
Customer deposits	577,604	(85,674)
Net cash provided by operating activities	23,086,514	23,258,163
Cash Flows from Investing Activities:
Purchases of investments	(18,449,755)	(6,235,399)
Proceeds from call / maturity of investments	6,625,000	8,137,561
Purchases of property and equipment	(1,174,420)	(887,609)
Proceeds from disposal of fixed assets	33,909
Purchases of intangible assets	(271,144)	(337,863)
Net cash provided by (used in) investing activities	(13,236,410)	676,690
Cash Flows from Financing Activities:
Repurchase of common stock	(24,999,767)	(19,995,950)
Proceeds from options exercised	10,219,289	730,473
Payroll tax payments for net-settled stock awards	(220,967)
Excess tax benefit from stock-based compensation	4,057,773
Payments on capital lease obligation	(25,262)
Net cash used in financing activities	(10,968,934)	(19,265,477)
Effect of exchange rate change on cash and cash equivalents	(2,467)	(4,398)
Net increase (decrease) in cash and cash equivalents	(1,121,297)	4,664,978
Cash and cash equivalents, beginning of period	36,126,791	21,300,733
Cash and cash equivalents, end of period	35,005,494	25,965,711
Supplemental Disclosure:
Cash paid for income taxes-net	2,426,978	864,461
Non-Cash Transactions:
Property and equipment purchases in accounts payable	$ 58,928	$ 34,168