CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $)
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Cash flows from operating activities:      
Net income (loss) $ (17,177,333) $ (14,059,539) $ 29,099,579
Adjustments to reconcile net income (loss) to net cash used in operating activities      
Depreciation and other amortization 463,137 419,358 568,288
Increase (decrease) in fair value of warrants (73,756) 804,516 24,436,309
Stock-based compensation 2,263,506 1,779,515 12,463,772
Other noncash income (expense) 48,774 0 0
Changes in assets and liabilities:      
Accounts receivable 3,759,484 (2,104,404) 365,041
Inventory (2,873,427) (17,641,922) 0
Deferred costs (19,741,668) (2,591,462) (250,072)
Prepaid expenses and other current assets 188,101 (444,251) 12,119
Other assets 147,621 (548,419) (4,697)
Deferred income taxes, net (9,599,927) (7,847,802) (36,051,978)
Accounts payable, accrued expenses and other current liabilities (4,566,993) 7,550,989 2,659,597
Deferred revenue 105,170,169 16,050,910 41,001,110
Other liabilities 281,302 18,717 147,586
Net cash provided by (used in) operating activities 58,436,502 (20,222,826) 25,574,036
Cash flows from investing activities:      
Capital expenditures (857,341) (588,235) (237,023)
Collateral for surety bond 0 (1,347,956) 0
Proceeds from maturity of short term investments 0 0 40,000,000
Purchases of short term investments 0 0 (25,004,717)
Net cash (used in) provided by investing activities (857,341) (1,936,191) 14,758,260
Cash flows from financing activities:      
Net proceeds from exercise of warrants and options 2,868,387 9,577 3,946,237
Payment of common stock tendered for employee tax obligations (178,952) 0 (1,353,656)
Proceeds from issuance of long-term debt 7,000,000 4,910,000 0
Repayments of long-term debt (8,000,000) 0 0
Excess tax benefit from share-based compensation 23,668 0 0
Net cash provided by financing activities 1,713,103 4,919,577 2,592,581
Net increase (decrease) in cash and cash equivalents 59,292,264 (17,239,440) 42,924,877
Cash and cash equivalents at beginning of period 32,017,490 49,256,930  
Cash and cash equivalents at end of period 91,309,754 32,017,490 49,256,930
Supplemental disclosure of non-cash financing activities:      
Reclass of common stock warrant liability to additional paid-in capital upon warrant exercise $ 751,370 $ 0 $ 9,531,911