Financial Instruments	6 Months Ended
Jun. 30, 2017
Equity [Abstract]
Financial Instruments	7. Financial Instruments 2016 Warrant On September 2, 2016, in connection with the entry into the Loan Agreement (see Note 8 for additional information), the Company issued a warrant (the “Warrant”) to the Lender to purchase a number of shares of the Company’s common stock equal to $4.0 million divided by the lower of (i) $2.29 per share and (ii) the subscription price paid in connection with the Rights Offering. The Warrant provides for weighted average anti-dilution protection and is exercisable in whole or in part for ten (10) years from the date of issuance. The subscription price paid was $1.50 in connection with the Rights Offering; accordingly, the exercise price of the Warrant has been set at $1.50 per share. The Company accounted for the Warrant in accordance with the authoritative guidance which requires that free-standing derivative financial instruments with certain anti-dilution features be classified as assets or liabilities at the time of the transaction, and recorded at their fair value. Any changes in the fair value of the derivative instruments are reported in earnings or loss as long as the derivative contracts are classified as assets or liabilities. Accordingly, the Company classified the Warrant as a liability and reported the change in fair value in the statement of operations. On September 2, 2016, the issuance date of the Warrant, the fair value of the liability classified Warrant was $5.8 million. The Company applied a Monte Carlo Simulation-model to calculate the fair value of the liability classified Warrant using the following assumptions: risk free interest rate of 1.60%; no dividend yield; an expected life of 10 years; and a volatility factor of 80%. The Company compared the Monte Carlo simulation model calculation to a Black-Scholes model calculation. These models generated substantially equal fair values for the Warrant. As such, the Company utilized a Black-Scholes model for June 30, 2017 to determine the fair value of the Warrant. As of June 30, 2017, the fair value of the Warrant was $7.1 million. A Black Scholes model was applied to calculate the fair value of the liability classified Warrant using the following assumptions: risk free interest rate of 2.28%; no dividend yield; an expected life of 9.17 years; and a volatility factor of 80%. For the three and six months ended June 30, 2017, the Company recorded a gain of $294,356 and a loss of $331,853, respectively as a result of the change in fair value of the liability classified Warrant. Rights Offering On November 16, 2016, the Company completed a rights offering (the “Rights Offering”), pursuant to which it raised approximately $35.3 million in gross proceeds through the sale of 23,523,195 shares of its common stock. The Rights Offering was made pursuant to a registration statement on Form S-1 filed with the Securities and Exchange Commission (the “SEC”) and declared effective by the SEC on October 21, 2016. As part of the Rights Offering, each stockholder of the Company received subscription right for each share of common stock owned as of the record date of October 12, 2016. Each subscription right entitled its holder to invest $0.65 towards the purchase of shares of the Company's common stock at a subscription price equal to the lower of $1.50 or 85% of the volume weighted average price of Company shares during market hours on the expiration date of the Rights Offering. The Rights Offering expired at 5:00 pm, New York City time, on November 8, 2016. Through basic subscriptions and oversubscriptions, the Rights Offering was fully subscribed. The subscription price was set at $1.50. The Company used the net proceeds of the Rights Offering, together with proceeds from the Loan Agreement and cash on hand, to fully satisfy PharmAthene's claim under the plan of reorganization. Rights Offering - Backstop Agreement On October 13, 2016, in connection with the Rights Offering as discussed above, the Company entered into an investment agreement or “backstop agreement”, with an affiliate of MacAndrews & Forbes Incorporated (“M&F”), and certain other backstop parties (the “Backstop Parties”). Under the terms of the backstop agreement, the Backstop Parties agreed to purchase, pursuant to a separate private placement, a number of shares of common stock equal to the numbers of shares that were not subscribed for in the Rights Offering. The backstop agreement provided that the subscription price for the Backstop Parties would be equal to the subscription price applicable to all shareholders under the Rights Offering. Because the Rights Offering was fully subscribed, the Backstop Parties were not required to draw on such commitment. The Company issued 708,530 shares to Backstop Parties, of which approximately 565,000 shares were received by M&F, in payment of the five percent backstop fee ($1,764,240) payable to the Backstop Parties in connection with the backstop agreement. When shares were issued to the Backstop Parties in payment of the backstop fee, the stock price of SIGA common stock was $2.49 per share (the closing price of the Company’s common stock on November 16, 2016). The fair value of the shares issued in satisfaction of the backstop fee was expensed to the income statement in the fourth quarter of 2016. There are no remaining payment obligations to the Backstop Parties under the Backstop Agreement.

7. Financial Instruments

2016 Warrant

On September 2, 2016, in connection with the entry into the Loan Agreement (see Note 8 for additional information), the Company issued a warrant (the “Warrant”) to the Lender to purchase a number of shares of the Company’s common stock equal to $4.0 million divided by the lower of (i) $2.29 per share and (ii) the subscription price paid in connection with the Rights Offering. The Warrant provides for weighted average anti-dilution protection and is exercisable in whole or in part for ten (10) years from the date of issuance. The subscription price paid was $1.50 in connection with the Rights Offering; accordingly, the exercise price of the Warrant has been set at $1.50 per share.

The Company accounted for the Warrant in accordance with the authoritative guidance which requires that free-standing derivative financial instruments with certain anti-dilution features be classified as assets or liabilities at the time of the transaction, and recorded at their fair value. Any changes in the fair value of the derivative instruments are reported in earnings or loss as long as the derivative contracts are classified as assets or liabilities. Accordingly, the Company classified the Warrant as a liability and reported the change in fair value in the statement of operations.

On September 2, 2016, the issuance date of the Warrant, the fair value of the liability classified Warrant was $5.8 million. The Company applied a Monte Carlo Simulation-model to calculate the fair value of the liability classified Warrant using the following assumptions: risk free interest rate of 1.60%; no dividend yield; an expected life of 10 years; and a volatility factor of 80%. The Company compared the Monte Carlo simulation model calculation to a Black-Scholes model calculation. These models generated substantially equal fair values for the Warrant. As such, the Company utilized a Black-Scholes model for June 30, 2017 to determine the fair value of the Warrant.

As of June 30, 2017, the fair value of the Warrant was $7.1 million. A Black Scholes model was applied to calculate the fair value of the liability classified Warrant using the following assumptions: risk free interest rate of 2.28%; no dividend yield; an expected life of 9.17 years; and a volatility factor of 80%.

For the three and six months ended June 30, 2017, the Company recorded a gain of $294,356 and a loss of $331,853, respectively as a result of the change in fair value of the liability classified Warrant.

Rights Offering

On November 16, 2016, the Company completed a rights offering (the “Rights Offering”), pursuant to which it raised approximately $35.3 million in gross proceeds through the sale of 23,523,195 shares of its common stock. The Rights Offering was made pursuant to a registration statement on Form S-1 filed with the Securities and Exchange Commission (the “SEC”) and declared effective by the SEC on October 21, 2016. As part of the Rights Offering, each stockholder of the Company received subscription right for each share of common stock owned as of the record date of October 12, 2016. Each subscription right entitled its holder to invest $0.65 towards the purchase of shares of the Company's common stock at a subscription price equal to the lower of $1.50 or 85% of the volume weighted average price of Company shares during market hours on the expiration date of the Rights Offering. The Rights Offering expired at 5:00 pm, New York City time, on November 8, 2016. Through basic subscriptions and oversubscriptions, the Rights Offering was fully subscribed. The subscription price was set at $1.50. The Company used the net proceeds of the Rights Offering, together with proceeds from the Loan Agreement and cash on hand, to fully satisfy PharmAthene's claim under the plan of reorganization.

Rights Offering - Backstop Agreement

On October 13, 2016, in connection with the Rights Offering as discussed above, the Company entered into an investment agreement or “backstop agreement”, with an affiliate of MacAndrews & Forbes Incorporated (“M&F”), and certain other backstop parties (the “Backstop Parties”). Under the terms of the backstop agreement, the Backstop Parties agreed to purchase, pursuant to a separate private placement, a number of shares of common stock equal to the numbers of shares that were not subscribed for in the Rights Offering. The backstop agreement provided that the subscription price for the Backstop Parties would be equal to the subscription price applicable to all shareholders under the Rights Offering. Because the Rights Offering was fully subscribed, the Backstop Parties were not required to draw on such commitment. The Company issued 708,530 shares to Backstop Parties, of which approximately 565,000 shares were received by M&F, in payment of the five percent backstop fee ($1,764,240) payable to the Backstop Parties in connection with the backstop agreement. When shares were issued to the Backstop Parties in payment of the backstop fee, the stock price of SIGA common stock was $2.49 per share (the closing price of the Company’s common stock on November 16, 2016). The fair value of the shares issued in satisfaction of the backstop fee was expensed to the income statement in the fourth quarter of 2016. There are no remaining payment obligations to the Backstop Parties under the Backstop Agreement.