Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $)	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Cash flows from operating activities:
Net income	$ 3,515,557us-gaap_NetIncomeLoss	$ 15,030,253us-gaap_NetIncomeLoss
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	913,859us-gaap_DepreciationAndAmortization	1,198,799us-gaap_DepreciationAndAmortization
Stock-based compensation expense	554,597us-gaap_ShareBasedCompensation	427,823us-gaap_ShareBasedCompensation
Deferred income taxes	(177,123)us-gaap_DeferredIncomeTaxExpenseBenefit	(323,669)us-gaap_DeferredIncomeTaxExpenseBenefit
Provision for inventory	29,922us-gaap_InventoryWriteDown	31,778us-gaap_InventoryWriteDown
Tax benefit from exercise of stock options	(933,863)	(4,436,249)
Changes in operating assets and liabilities:
Accounts receivable	761,041	2,140,848
Inventories	(284,016)us-gaap_IncreaseDecreaseInInventories	(2,016,631)us-gaap_IncreaseDecreaseInInventories
Prepaid expenses, other current and long-term assets	476,935	(345,415)
Prepaid income taxes	(1,198,483)us-gaap_IncreaseDecreaseInPrepaidTaxes
Accounts payable	632,521	51,712
Accrued expenses	(374,682)	(1,104,945)
Deferred revenue	111,697	(2,113,086)
Income taxes payable		5,099,027
Other long-term liabilities	(44,128)	(43,588)
Net cash provided by operating activities	3,983,834	13,596,657
Cash flows from investing activities:
Proceeds from maturity of investments	1,500,000
Purchase of investments	(7,250,000)
Purchase of property and equipment	(256,020)	(276,513)
Net cash used in investing activities	(6,006,020)	(276,513)
Cash flows from financing activities:
Proceeds from exercise of stock options	963,582	1,067,767
Tax benefit from exercise of stock options	933,863	4,436,249
Net cash provided by financing activities	1,897,445	5,504,016
Exchange rate impact on cash	(228,918)	2,931
(Decrease) increase in cash and cash equivalents	(353,659)	18,827,091
Cash and cash equivalents at beginning of period	100,155,864	63,333,160
Cash and cash equivalents at end of period	$ 99,802,205	$ 82,160,251

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Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.