Stock options, strike price description.

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- Definition

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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- Definition

Aggregate number of common shares reserved for future issuance.

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- Definition

Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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- Definition

Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

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- Definition

Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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- Definition

Number of shares authorized for issuance under share-based payment arrangement.

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- Definition

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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- Definition

Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

+ References

No definition available.

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- Definition

Number of shares of stock issued as of the balance sheet date, including shares that had been issued and were previously outstanding but which are now held in the treasury.

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Stock-Based Compensation (Details Narrative) - USD ($)			3 Months Ended
Stock-Based Compensation (Details Narrative) - USD ($)	Feb. 19, 2019	Sep. 28, 2018	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Jun. 15, 2020
Weighted average exercise price, options granted			$ 2.24	$ 1.01
Unrecognized compensation cost related to non-vested stock based compensation			$ 4,100,000
Stock based compensation cost expected to be recognized, weighted average period			1 year 3 months 19 days
Equity Stock Awards [Member] \| Granted Under 2018 Plan and 2007 Plan [Member]
Number of shares reserved for future issuance			6,420,825
Inducement Awards [Member]
Number of shares reserved for future issuance					140,004
Stock Options and Restricted Stock Awards [Member]
Compensation cost			$ 1,600,000	$ 500,000
Stock Options and Restricted Stock Awards [Member] \| Research and Development Expense [Member]
Compensation cost			587,507	177,936
Stock Options and Restricted Stock Awards [Member] \| General and Administrative Expense [Member]
Compensation cost			$ 991,819	$ 274,029
2018 Stock Incentive Plan [Member]
Equity awards, number of stock authorized			2,700,000
Number of shares reserved for future issuance			6,498,424
2018 Stock Incentive Plan [Member] \| Minimum [Member]
Number of equity awards available for future issuance			1,200,000			2,500,000
2018 Stock Incentive Plan [Member] \| Maximum [Member]
Number of equity awards available for future issuance			3,900,000			6,400,000
2007 Stock Incentive Plan [Member]
Stock options, strike price description			Options are generally granted with strike prices equal to the fair market value of a share of Celsion common stock on the date of grant. Incentive stock options may be granted to purchase shares of common stock at a price not less than 100% of the fair market value of the underlying shares on the date of grant, provided that the exercise price of any incentive stock option granted to an eligible employee owning more than 10% of the outstanding stock of Celsion must be at least 110% of such fair market value on the date of grant. Only officers and key employees may receive incentive stock options.
Inducement Option Grants [Member] \| Five New Employees [Member]
Weighted average exercise price, options granted	$ 2.18	$ 2.77
Option vested period	3 years	3 years
Inducement Option Grants [Member] \| Five New Employees [Member] \| Restricted Stock [Member]
Number of shares issued	13,000	19,000
Inducement Option Grants [Member] \| Five New Employees [Member] \| Common Stock Outstanding [Member]
Number of shares issued	140,004	164,004
2018 Plan [Member]
Number of shares reserved for future issuance					77,599