Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($)	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Cash flows from operating activities:
Net income	$ 11,335,114	$ 24,332,603
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	1,827,070	2,366,411
Stock-based compensation expense	1,063,949	805,782
Deferred income taxes	(428,312)	(357,081)
Provision for inventory	67,863	147,693
Tax benefit from exercise of equity awards	(933,863)	(9,308,113)
Changes in operating assets and liabilities:
Accounts receivable	(2,389,372)	(191,088)
Inventories	496,543	(3,030,077)
Prepaid expenses, other current and long-term assets	458,857	(10,624)
Accounts payable	559,363	(943,169)
Accrued expenses	(263,692)	(749,411)
Deferred revenue	(5,480)	(2,140,902)
Income taxes payable	3,193,594	7,014,770
Other long-term liabilities	(97,679)	(99,980)
Net cash provided by operating activities	14,883,955	$ 17,836,814
Cash flows from investing activities:
Proceeds from maturity of investments	10,250,000
Purchase of investments	(22,018,070)
Purchase of property and equipment	(1,133,972)	$ (677,358)
Net cash used in investing activities	(12,902,042)	(677,358)
Cash flows from financing activities:
Proceeds from exercise of equity awards	969,029	1,361,805
Tax benefit from exercise of stock options	$ 933,863	9,308,113
Minimum tax withholdings on share-based awards		(6,348,900)
Net cash provided by financing activities	$ 1,902,892	4,321,018
Exchange rate impact on cash	(120,447)	65,928
Increase in cash and cash equivalents	3,764,358	21,546,402
Cash and cash equivalents at beginning of period	100,155,864	63,333,160
Cash and cash equivalents at end of period	$ 103,920,222	$ 84,879,562