Statement of Financial Position [Abstract] Cash and cash equivalents Cash and cash equivalents at beginning of period Cash and cash equivalents at end of period Investment securities – available for sale, at fair value Total Short-term Investments Accrued interest receivable on investment securities Advances, deposits and other current assets Total current assets Property and equipment (at cost, less accumulated depreciation of $1,520,690 and $1,264,190, respectively) Accumulated depreciation (in Dollars) Finite-Lived Intangible Assets by Major Class [Axis] In Process Research and Development [Member] Finite lived intangible assets, net In-process research and development Goodwill Deposits, deferred fees and other assets Patents [Member] Total other assets Total assets Accounts payable Accrued liabilities Total accrued liabilities Notes payable – current portion Deferred revenue – current portion Total current liabilities Earnout milestone liability Common stock warrant liability Common Stock Warrant Liability Common Stock Warrant Liability Notes payable, net of discounts Deferred revenue Other non-current liabilities Total liabilities Preferred stock, $0.01 par value: 100,000 shares authorized; no shares issued or outstanding at September 30, 2014 and December 31, 2013, respectively Preferred stock, par value (in Dollars per share) Preferred stock, shares authorized Preferred stock, shares issued Preferred stock, shares outstanding Common stock, $0.01 par value; 75,000,000 shares authorized; 20,097,103 and 13,737,970 shares issued at September 30, 2014 and December 31, 2013, and 19,976,046 and 13,604,975 shares outstanding at September 30, 2014 and December 31, 2013, respectively Common stock, par value (in Dollars per share) Common Stock, Par or Stated Value Per Share (in Dollars per share) Common stock, shares authorized Common Stock, Shares Authorized (in Shares) Common stock, shares issued Common stock, shares outstanding Common Stock, Shares, Outstanding Additional paid-in capital Accumulated other comprehensive loss Balance Balance Accumulated deficit Subtotal Treasury stock, at cost (121,057 and 132,995 shares at September 30, 2014 and December 31, 2013, respectively) Treasury stock, shares Total stockholders' equity Total liabilities and stockholders' equity Income Statement [Abstract] Licensing revenue Research and development General and administrative Acquisition costs Business Combination, Acquisition Related Costs Total operating expenses Operating Expenses Loss from operations Gain (loss) from change in valuation of common stock warrant liability Investment income, net Investment income, net Interest expense Other income (expense) Total other (expense) income, net Net loss Net loss Net loss Non-cash deemed dividend from beneficial conversion feature on convertible preferred stock Net loss attributable to common shareholders Basic and diluted (in Dollars per share) Basic and diluted (in Shares) Statement of Comprehensive Income [Abstract] Realized (gain) loss on investment securities recognized in investment income, net Realized loss reclassified from other accumulated comprehensive loss Unrealized loss on investment securities Other comprehensive (loss) gain Net other comprehensive loss, net Comprehensive loss Statement of Cash Flows [Abstract] Depreciation and amortization Change in fair value of common stock warrant liability Gain from the adjustment for the change in fair value included in net income Cash received for non-refundable technology transfer fee Deferred revenue Stock-based compensation Treasury shares issued for services and 401(k) matching contributions Change in deferred rent liability Amortization of deferred finance charges and debt discount associated with notes payable Loss on sale of investment securities Accrued interest on short term investments and other current assets Accounts payable Accrued liabilities Net cash used in operating activities: Purchases of investment securities Proceeds from sale and maturity of investment securities Cash used in acquisition of EGEN, Inc. (net of cash received) Cash, net of cash acquired Refund of deposit for letter of credit Purchases of property and equipment Net cash used in investing activities Proceeds from sale of common stock equity, net of issuance costs Proceeds from Issuance of Common Stock (in Dollars) Proceeds from sale of preferred stock, net of issuance costs Proceeds from exercise of common stock warrants Proceeds from exercise of options to purchase common stock Proceeds from note payable Principal payments on notes payable Net cash provided by financing activities Decrease in cash and cash equivalents Interest paid Business Acquisition [Axis] EGEN, Inc. [Member] Fair value of common stock issued in acquisition of EGEN, Inc. assets Disclosure Text Block [Abstract] Earnings Per Share [Abstract] Investments, Debt and Equity Securities [Abstract] Short-Term Investment by Bond Maturities [Abstract] Major Types of Debt and Equity Securities [Axis] Corporate Bond Maturing Within 3 Months [Member] Cost Fair value Corporate Bond Maturing Between 3 and 12 Months [Member] Investment Securities Gross Unrealized Losses and Fair Value by Investment Category [Abstract] Corporate Debt Securities [Member] Bonds – corporate issuances with unrealized gains Bonds – corporate issuances with unrealized gains Bonds – corporate issuances with unrealized losses Bonds – corporate issuances with unrealized losses Total Investment Income [Abstract] Interest and dividend income Realized gains (losses) Component of Accumulated Other Comprehensive Loss [Abstract] Equity Components [Axis] Accumulated Net Unrealized Investment Gain (Loss) [Member] Unrealized losses on investment securities Fair Value Disclosures [Abstract] Assets and Liabilities at Fair Value on a Recurring Basis [Abstract] Measurement Frequency [Axis] Fair Value, Measurements, Recurring [Member] Short-term investments available for sale Bonds – corporate issuances Fair Value, Measurements, Nonrecurring [Member] Common stock warrant liability Fair Value, Hierarchy [Axis] Fair Value, Inputs, Level 1 [Member] Fair Value, Inputs, Level 2 [Member] Fair Value, Inputs, Level 3 [Member] Business Combinations [Abstract] Fair Value of Consideration [Abstract] Celsion common stock (2,712,188 shares valued at $3.48 which was the last closing price of our common stock at the time of closing the transaction on June 20, 2014) Common Stock, shares issued Common Stock, price per share (in Dollars per share) Share Price (in Dollars per share) Holdback Shares (670,070 shares of Celsion common stock which were discounted by 38% to reflect the cost of the restriction) Common Stock, shares to be issued Business Acquisition, Equity Interest Issued or Issuable, Number of Shares (in Shares) Common Stock, discount Earnout Payments (at fair value*) Business Combination, Consideration Transferred, Liabilities Incurred Total fair value of consideration Business Combination, Consideration Transferred Summary of Estimated Fair Values of Acquired Assets and Liabilities [Abstract] Property and equipment, net In-process research and development Total assets: Accounts payable and accrued liabilities Net assets acquired Pro Forma Information [Abstract] Revenues Loss from operations Net loss applicable to common stock Goodwill and Intangible Assets Disclosure [Abstract] Summary of Goodwill and IPR&D [Abstract] Total goodwill and in-process research and development Payables and Accruals [Abstract] Accrued Liabilities [Abstract] Amounts due to contract research organizations and other contractual agreements Contractual Obligation Accrued payroll and related benefits Accrued professional fees Accrued interest on notes payable Other Debt Disclosure [Abstract] Future Principal Payments Due on the Credit Agreement [Abstract] 2015 2016 2017 2018 and thereafter Total Debt Instrument [Axis] Hercules Credit Agreement [Member] Stockholders' Equity Note [Abstract] Plan Name [Axis] Prefered Stock [Member] Assumptions Used in the Valuation of the Warrants Associated with Preferred Stock Offering [Abstract] Risk-free interest rate Expected volatility Expected life (in years) Expected forfeiture rate Expected forfeiture rate Expected dividend yield Warrant [Member] Disclosure of Compensation Related Costs, Share-based Payments [Abstract]