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Notes and Loans Payable (Details Narrative) - USD ($)						1 Months Ended	3 Months Ended		9 Months Ended
	Aug. 28, 2020	Jun. 22, 2020	May 26, 2020	Apr. 23, 2020	Jun. 27, 2018	Sep. 30, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
warrants exercise per share						$ 0.01	$ 0.01		$ 0.01
Debt financing fees						$ 43,463	$ 43,463		$ 43,463
Loan amount						$ 5,000,000	5,000,000		5,000,000
Common stock shares issued						2,000,000
Net proceeds from issuance of common stock						$ 1,500,000			20,250,426	$ 6,175,527
Initial Horizon Credit Agreement Amendment [Member]
Interest expense, debt, total							198,738	$ 252,144	685,913	760,615
Amortization of debt issuance costs							251,993	$ 97,458	444,786	$ 289,182
Common Stock [Member]
Common stock shares issued		2,666,667
Net proceeds from issuance of common stock		$ 9,100,000
Initial Horizon Credit Agreement [Member]
Proceeds from lines of credit, total					$ 10,000,000
Initial Horizon Credit Agreement [Member] | Common Stock [Member]
Warrants exercisable					190,114
warrants exercise per share					$ 2.63
Warrants outstanding					95,057
Amendment to Horizon Credit Agreement [Member] | Horizon Technology Finance Corporation [Member]
Repayment of loans	$ 5,000,000
Debt instrument related end term charges	200,000
Debt instrument face amount	$ 5,000,000
Debt instrument, interest rate terms	The obligations bear interest at a rate calculated based an amount by which the one-month LIBOR exceeds 2% plus 9.625%. In no event shall the interest rate be less than 9.625%. Payments pursuant to the Amendment are 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.
Debt instrument, end term fee	$ 275,000
Debt instrument, restrictive covenants	In addition, pursuant to the Amendment, Celsion has agreed to provide evidence to Horizon on or before March 31, 2021, that it has 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.
Payment of debt extinguishment	$ 5,000,000
Debt instrument, unamortized discount	200,000					$ 109,706	$ 109,706		$ 109,706
Debt financing fees	5,000
New warrants fair value	$ 247,548
Amendment to Horizon Credit Agreement [Member] | Horizon Technology Finance Corporation [Member] | Common Stock [Member]
Warrants exercisable	247,525
warrants exercise per share	$ 1.01
Warrants cancelled	95,057
Amendment to Horizon Credit Agreement [Member] | Horizon Technology Finance Corporation [Member] | One-Month LIBOR Exceeds 2% Plus [Member]
Debt instrument interest rate	96.25%
April PPP Loan [Member] | Silicon Valley Bank [Member]
Proceeds from loan				$ 632,220
Loan repayment date				May 13, 2020
PPP Loans [Member] | Silicon Valley Bank [Member] | Maximum [Member]
Loan amount				$ 2,000,000
May PPP Loan [Member] | Silicon Valley Bank [Member]
Proceeds from loan			$ 692,530
Loan repayment date			Jun. 24, 2020
Interest accrued on loan			$ 577
May PPP Loan [Member] | Silicon Valley Bank [Member] | Promissory Note [Member]
Debt instrument face amount			$ 692,530

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