Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities:
Net loss	$ (24,338,804)	$ (20,658,846)	$ (35,151,715)
Adjustments to reconcile net loss to net cash used in operating activities:
Share-based compensation expense	2,519,750	3,658,874	2,624,742
Depreciation and amortization	1,860,682	1,569,848	1,224,217
Loss on disposal of equipment	261,814	167,097	39,983
Write-off of capitalized patent costs	0	31,501	0
Increase in inventory reserve	748,378	700,000	3,550,000
Amortization of premiums and discounts	12,225	10,313	20,036
Changes in operating assets and liabilities:
Accounts receivable	(1,137,543)	(4,422,689)	(2,478,494)
Inventories	(350,943)	(564,473)	(2,948,873)
Prepaid expenses and other current assets	1,921,937	(934,356)	(617,121)
Deferred costs	(574,229)	714,704	(1,538,148)
Other assets	100,000	148,000	545,059
Accounts payable	2,858,884	(3,494,536)	2,688,054
Accrued expenses and other liabilities	(582,295)	905,882	221,086
Deferred revenue	1,505,202	(6,030,160)	5,487,873
Net cash used in operating activities	(15,194,942)	(28,198,841)	(26,333,301)
Cash flows from investing activities:
Purchases of equipment, molds, furniture and fixtures	(4,879,509)	(5,643,043)	(4,663,313)
Additions to patent rights	(127,156)	(1,043,628)	(989,790)
Proceeds from maturities of investment securities	15,000,000	6,000,000	24,000,000
Purchases of investment securities		(15,037,675)
Net cash provided by (used in) investing activities	9,993,335	(15,724,346)	18,346,897
Cash flows from financing activities:
Proceeds from issuance of common stock, net		42,850,677
Proceeds from exercise of stock options and warrants	101,092	30,800	3,105,102
Taxes paid related to net share settlement of equity awards	(83,631)	(87,770)	(154,397)
Net cash provided by financing activities	17,461	42,793,707	2,950,705
Effect of exchange rate changes on cash	58	(733)	(2,648)
Net decrease in cash and cash equivalents	(5,184,088)	(1,130,213)	(5,038,347)
Cash and cash equivalents:
Beginning of year	32,898,676	34,028,889	39,067,236
End of year	27,714,588	32,898,676	34,028,889
Supplemental disclosure of non-cash investing activities:
Purchases of equipment, molds, furniture and fixtures recorded in accounts payable and accrued expenses	424,389	641,379	1,118,925
Additions to patent rights recorded in accounts payable and accrued expenses	$ 44,589	$ 21,027	$ 949,631