Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($)	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Cash flows from operating activities:
Net income	$ 19,714,979	$ 30,503,403
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	2,800,158	3,576,441
Stock-based compensation expense	1,562,391	$ 1,196,361
Deferred income taxes	(15,873)
Provision for inventory	147,560	$ 220,207
Tax benefit from equity awards	(876,797)	(9,236,708)
Changes in operating assets and liabilities:
Accounts receivable	(6,549,905)	(1,840,407)
Inventories	82,360	(2,923,628)
Prepaid expenses, other current and long-term assets	403,211	183,481
Accounts payable	970,373	(992,822)
Accrued expenses	(120,334)	(989,291)
Deferred revenue	(9,135)	(2,078,543)
Income taxes payable	5,756,972	7,771,001
Other long-term liabilities	(75,777)	(167,123)
Net cash provided by operating activities	23,790,183	$ 25,222,372
Cash flows from investing activities:
Proceeds from maturity of investments	14,750,000
Purchase of investments	(30,008,761)	$ (19,999,169)
Purchase of property and equipment	(2,028,093)	(920,132)
Net cash used in investing activities	(17,286,854)	(20,919,301)
Cash flows from financing activities:
Proceeds from exercise of equity awards	1,074,814	1,379,294
Tax benefit from equity awards	$ 876,797	9,236,708
Minimum tax withholdings on share-based awards		(6,348,900)
Net cash provided by financing activities	$ 1,951,611	4,267,102
Exchange rate impact on cash	(141,783)	(131,139)
Increase in cash and cash equivalents	8,313,157	8,439,034
Cash and cash equivalents at beginning of period	100,155,864	63,333,160
Cash and cash equivalents at end of period	108,469,021	71,772,194
Noncash Investing Activities:
Purchases of property and equipment included in accounts payable and accrued expenses	$ 2,197,088	$ 215,783