Common Stock	3 Months Ended
Mar. 31, 2017
Text Block [Abstract]
Common Stock	8. Common Stock Registered Direct Offering On January 27, 2017, the Company entered into a Securities Purchase Agreement (the “Purchase Agreement”) with certain investors for the sale by the Company of 2,000,000 shares of the Company’s common stock at a purchase price of $2.50 per share in a registered direct offering. The closing of the sale of the shares under the Purchase Agreement occurred on February 2, 2017. On February 3, 2017, Pulmatrix, Inc. entered into a Securities Purchase Agreement (the “Second Purchase Agreement”) with certain investors for the sale by the Company of 950,000 shares of the Company’s common stock at a purchase price of $3.50 per share in a registered direct offering. The closing of the sale of the shares under the Second Purchase Agreement occurred on February 8, 2017. Net of commissions and other issuance costs totaling $727, aggregate net proceeds of the two noted registered direct offerings were $7,598. The shares were offered and sold by the Company pursuant to an effective shelf registration statement on Form S-3, which was filed with the Securities and Exchange Commission on July 15, 2016, and subsequently declared effective on August 3, 2016 (File No. 333-212546), and a related prospectus. At-the-Market Offering On March 17, 2017, the Company entered into an At-The-Market Sales Agreement (the “Sales Agreement”) with BTIG, LLC (“BTIG”) to act as the Company’s sales agent with respect to the issuance and sale of up to $11,000,000 of the Company’s shares of common stock, from time to time in an at-the-market public offering (the “Offering”). Sales of common stock under the Sales Agreement are made pursuant to an effective shelf registration statement on Form S-3, which was filed with the Securities and Exchange Commission on July 15, 2016, and subsequently declared effective on August 3, 2016 (File No. 333-212546), and a related prospectus. BTIG acts as the Company’s sales agent on a commercially reasonable efforts basis, consistent with its normal trading and sales practices and applicable state and federal laws, rules and regulations and the rules of The NASDAQ Global Market. If expressly authorized by the Company, BTIG may also sell the Company’s common stock in privately negotiated transactions. There is no specific date on which the Offering will end, there are no minimum sale requirements and there are no arrangements to place any of the proceeds of this offering in an escrow, trust or similar account. BTIG is entitled to compensation at a fixed commission rate of 3.0% of the gross proceeds from the sale of the Company’s common stock pursuant to the Sales Agreement. During the three month period ended March 31, 2017, the Company sold 538,427 shares of its common stock under the Sales Agreement at an average selling price of approximately $4.04 per share which resulted in gross proceeds of approximately $2,175 and net proceeds of approximately $2,104 after payment of 3% commission to BTIG and other issuance costs. Approximately $108 of these proceeds were classified in stock subscriptions receivable as of March 31, 2017 which were subsequently collected in April 2017.

8. Common Stock

Registered Direct Offering

On January 27, 2017, the Company entered into a Securities Purchase Agreement (the “Purchase Agreement”) with certain investors for the sale by the Company of 2,000,000 shares of the Company’s common stock at a purchase price of $2.50 per share in a registered direct offering. The closing of the sale of the shares under the Purchase Agreement occurred on February 2, 2017.

On February 3, 2017, Pulmatrix, Inc. entered into a Securities Purchase Agreement (the “Second Purchase Agreement”) with certain investors for the sale by the Company of 950,000 shares of the Company’s common stock at a purchase price of $3.50 per share in a registered direct offering. The closing of the sale of the shares under the Second Purchase Agreement occurred on February 8, 2017.

Net of commissions and other issuance costs totaling $727, aggregate net proceeds of the two noted registered direct offerings were $7,598. The shares were offered and sold by the Company pursuant to an effective shelf registration statement on Form S-3, which was filed with the Securities and Exchange Commission on July 15, 2016, and subsequently declared effective on August 3, 2016 (File No. 333-212546), and a related prospectus.

At-the-Market Offering

On March 17, 2017, the Company entered into an At-The-Market Sales Agreement (the “Sales Agreement”) with BTIG, LLC (“BTIG”) to act as the Company’s sales agent with respect to the issuance and sale of up to $11,000,000 of the Company’s shares of common stock, from time to time in an at-the-market public offering (the “Offering”). Sales of common stock under the Sales Agreement are made pursuant to an effective shelf registration statement on Form S-3, which was filed with the Securities and Exchange Commission on July 15, 2016, and subsequently declared effective on August 3, 2016 (File No. 333-212546), and a related prospectus. BTIG acts as the Company’s sales agent on a commercially reasonable efforts basis, consistent with its normal trading and sales practices and applicable state and federal laws, rules and regulations and the rules of The NASDAQ Global Market. If expressly authorized by the Company, BTIG may also sell the Company’s common stock in privately negotiated transactions. There is no specific date on which the Offering will end, there are no minimum sale requirements and there are no arrangements to place any of the proceeds of this offering in an escrow, trust or similar account.

BTIG is entitled to compensation at a fixed commission rate of 3.0% of the gross proceeds from the sale of the Company’s common stock pursuant to the Sales Agreement.

During the three month period ended March 31, 2017, the Company sold 538,427 shares of its common stock under the Sales Agreement at an average selling price of approximately $4.04 per share which resulted in gross proceeds of approximately $2,175 and net proceeds of approximately $2,104 after payment of 3% commission to BTIG and other issuance costs. Approximately $108 of these proceeds were classified in stock subscriptions receivable as of March 31, 2017 which were subsequently collected in April 2017.