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Notes Payable (Details Narrative) - USD ($) |  |  | 1 Months Ended | 3 Months Ended | 9 Months Ended |
--- | --- | --- | --- | --- | --- | ---
Aug. 28, 2020 | Jun. 27, 2018 | Jun. 18, 2021 | Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020 | Jun. 30, 2021
Short-term Debt [Line Items] |  |  |  |  |  |  |  |
Interest and Debt Expense |  |  |  | $ 95,520 | $ 450,732 | $ 474,361 | $ 1,130,699 |
Debt Issuance Costs, Net |  |  |  | $ 191,226 |  | $ 191,226 |  |
Class of Warrant or Right, Exercise Price of Warrants or Rights |  |  |  | $ 0.01 |  | $ 0.01 |  |
Initial Horizon Credit Agreement Amendment [Member] |  |  |  |  |  |  |  |
Short-term Debt [Line Items] |  |  |  |  |  |  |  |
Amortization of Debt Issuance Costs |  |  |  |  | 251,993 | $ 139,428 | 444,786 |
Interest Expense, Debt |  |  |  |  | $ 198,738 | $ 225,920 | $ 685,913 |
Horizon Technology Finance Corporation [Member] |  |  |  |  |  |  |  |
Short-term Debt [Line Items] |  |  |  |  |  |  |  |
Long-term Line of Credit |  |  | $ 5,425,000 |  |  |  |  |
SVB Loan Facility [Member] |  |  |  |  |  |  |  |
Short-term Debt [Line Items] |  |  |  |  |  |  |  |
Line of Credit Facility, Maximum Borrowing Capacity |  |  | 10,000,000 |  |  |  |  |
Proceeds from Lines of Credit |  |  | 6,000,000 |  |  |  |  |
Restricted cash |  |  | 6,000,000.0 |  |  |  |  |
Line of Credit Facility, Remaining Borrowing Capacity |  |  | $ 4,000,000 |  |  |  |  |
Debt Instrument, Interest Rate, Stated Percentage |  |  | 3.25% |  |  |  |  |
Final payment percentage |  |  | 3.00% |  |  |  |  |
Long-term Line of Credit |  |  | $ 10,000,000 |  |  |  |  |
Debt Instrument, Description |  |  | Payments under the loan agreement are interest only for the first 24 months after loan closing, followed by a 24-month amortization period of principal and interest through the scheduled maturity date. |  |  | Payments under the loan agreement are interest only (calculated based on one-month LIBOR plus 7.625%) for the first 24 months through July 2020, followed by a 21-month amortization period of principal and interest starting on August 1, 2020 and ending through the scheduled maturity date |  |
Interest and Debt Expense |  |  | $ 243,370 |  |  |  |  |
End of term charge percentage |  |  | 3.00% |  |  |  |  |
Amortization of Debt Issuance Costs |  |  | $ 300,000 |  |  |  |  |
Interest Expense, Debt |  |  |  | $ 49,883 |  | $ 56,875 |  |
Amortization of Debt Issuance Costs and Discounts |  |  |  | $ 45,687 |  | 52,144 |  |
Initial Horizon Credit Agreement [Member] |  |  |  |  |  |  |  |
Short-term Debt [Line Items] |  |  |  |  |  |  |  |
Line of Credit Facility, Maximum Borrowing Capacity |  | $ 10,000,000 |  |  |  |  |  |
Proceeds from Lines of Credit |  | 10,000,000 |  |  |  |  |  |
Line of Credit Facility, Remaining Borrowing Capacity |  | 5,000,000 |  |  |  |  |  |
Interest and Debt Expense |  | $ 175,000 |  |  |  |  |  |
End of term charge percentage |  | 4.00% |  |  |  |  |  |
Debt Instrument, Fee Amount |  | $ 142,605 |  |  |  |  |  |
Loan Processing Fee |  | 100,000 |  |  |  |  |  |
Debt Instrument, Unamortized Discount |  | 782,116 |  |  |  |  |  |
Debt Issuance Costs, Net |  | 400,000 |  |  |  |  |  |
Fair Value Adjustment of Warrants |  | 507,116 |  |  |  |  |  |
End of term fees |  | $ 275,000 |  |  |  |  |  |
Initial Horizon Credit Agreement [Member] | Common Stock [Member] |  |  |  |  |  |  |  |
Short-term Debt [Line Items] |  |  |  |  |  |  |  |
Class of Warrant or Right, Number of Securities Called by Warrants or Rights |  | 190,114 |  |  |  |  |  |
Class of Warrant or Right, Exercise Price of Warrants or Rights |  | $ 2.63 |  |  |  |  |  |
Class of Warrant or Right, Outstanding |  | 95,057 |  |  |  |  |  |
Amendment to Horizon Credit Agreement [Member] | Horizon Technology Finance Corporation [Member] |  |  |  |  |  |  |  |
Short-term Debt [Line Items] |  |  |  |  |  |  |  |
Debt instrument related end term charges | $ 200,000 |  |  |  |  |  |  |
Debt instrument face amount | $ 5,000,000 |  |  |  |  |  |  |
Debt Instrument, Interest Rate Terms | The obligations bore interest at a rate calculated based an amount by which the one-month LIBOR exceeds 2% plus 7.625%. In no event shall the interest rate be less than 9.625%. Payments pursuant to the Amendment were interest only for the first twelve (12) months after August 1, 2020, followed by a 21-month amortization period of principal and interest through the scheduled maturity date on April 1, 2023. In addition, the remaining $5 million in obligations was subject to an end of term fee equal, in the aggregate, to $275,000, which amount was payable upon the maturity of the obligations or upon the date of final payment or default, as applicable. |  |  |  |  |  |  |
Payment for Debt Extinguishment or Debt Prepayment Cost | $ 5,000,000 |  |  |  |  |  |  |
Debt Instrument, Fee Amount | $ 275,000 |  |  |  |  |  |  |
Debt Instrument, Restrictive Covenants | In connection with the Amendment, Celsion agreed to a liquidity covenant which provides that, at all times, Celsion shall maintain unrestricted cash and/or cash equivalents on deposit in accounts over which the applicable Lenders maintain an account control agreement in an amount not less than $2.5 million. In addition, pursuant to the Amendment, Celsion agreed to provide evidence to Horizon on or before March 31, 2021, that it received aggregate cash proceeds of not less than $5 million from the sale of equity, debt, its New Jersey net operating losses, or a combination thereof, subsequent to the date of the Amendment. The Company met this requirement during the fourth quarter of 2020. |  |  |  |  |  |  |
Debt Instrument, Unamortized Discount | $ 200,000 |  |  |  |  |  |  | $ 109,706
Debt Issuance Costs, Net | 5,000 |  |  |  |  |  |  |
Warrants Not Settleable in Cash, Fair Value Disclosure | $ 247,548 |  |  |  |  |  |  |
Amendment to Horizon Credit Agreement [Member] | Horizon Technology Finance Corporation [Member] | Common Stock [Member] |  |  |  |  |  |  |  |
Short-term Debt [Line Items] |  |  |  |  |  |  |  |
Class of Warrant or Right, Number of Securities Called by Warrants or Rights | 247,525 |  |  |  |  |  |  |
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ 1.01 |  |  |  |  |  |  |
Warrants cancelled | 95,057 |  |  |  |  |  |  |
Horizon Credit Agreement [Member] |  |  |  |  |  |  |  |
Short-term Debt [Line Items] |  |  |  |  |  |  |  |
Interest Expense, Debt |  |  |  |  |  | 190,581 |  |
Gain (Loss) on Contract Termination |  |  |  |  |  | $ 234,419 |  |
Horizon Credit Agreement [Member] | Horizon Technology Finance Corporation [Member] |  |  |  |  |  |  |  |
Short-term Debt [Line Items] |  |  |  |  |  |  |  |
Debt instrument face amount | $ 10,000,000 |  |  |  |  |  |  |

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- Definition Amount of the cost of borrowed funds accounted for as interest expense for debt. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=123466204&loc=SL6036836-161870 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.8) -URI http://asc.fasb.org/extlink&oid=123367319&loc=SL114868664-224227 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 55 -Paragraph 69F -URI http://asc.fasb.org/extlink&oid=123466577&loc=SL123495745-112612 Reference 4: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 55 -Paragraph 69E -URI http://asc.fasb.org/extlink&oid=123466577&loc=SL123495743-112612 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 50 -Paragraph 1F -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495355-112611 + Details
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- Definition The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(22)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(16)) -URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(16)) -URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910 + Details
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- Definition Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
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- Definition Amount of cash inflow from contractual arrangement with the lender, including but not limited to, letter of credit, standby letter of credit and revolving credit arrangements. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3255-108585 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08(f)) -URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690 + Details
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