Debt	3 Months Ended
Sep. 30, 2018
Debt Disclosure [Abstract]
Debt	Debt Liability related to sale of future royalties: On January 7, 2018, the Company entered into a funding agreement with RPI Finance Trust, a Delaware statutory trust ("RPI"), under which we sold a portion of our right to receive royalties on potential net sales of the ADC sacituzumab govitecan, in exchange for $175.0 million in cash. Concurrently, we entered into a common stock purchase agreement with RPI through which RPI purchased 4.4 million shares of the Company's common stock for $75.0 million (the "Financing"). The Company concluded that there were two units of accounting in the transaction: (1) the Liability related to the sale of future royalties and (2) the "Financing". We allocated the consideration of $250.0 million on a relative fair value basis to the liability for $182.2 million and the common stock for $67.8 million. We continue to accrete the Liability related to the sale of future royalties using the interest method with an annual interest rate of approximately 19.3%. As of June 30, 2018, we determined the fair value at $202.0 million. During the three months ended September 30, 2018, the Company recognized $9.8 million in interest expense. Convertible Senior Notes: In February 2015, the Company issued $100.0 million of Convertible Senior Notes (the "Convertible Senior Notes") (net proceeds of approximately $96.3 million after deducting the initial purchasers’ fees and offering expenses) in a private offering exempt from registration under the Securities Act of 1933, as amended (the “Securities Act”), in reliance upon Rule 144A under the Securities Act. The Convertible Senior Notes will mature on February 15, 2020, unless earlier purchased or converted. The debt issuance costs of approximately $3.7 million, primarily consisting of underwriting, legal and other professional fees, are amortized over the term of the Convertible Senior Notes. The Convertible Senior Notes are senior unsecured obligations of the Company. Interest at 4.75% is payable semiannually on February 15 and August 15 of each year. The effective interest rate on the Convertible Senior Notes was 5.48% for the period from the date of issuance through September 30, 2018. The Convertible Senior Notes are convertible at the option of holders into approximately 19.6 million shares of common stock at any time prior to the close of business on the day immediately preceding the maturity date. The exchange rate will initially be 195.8336 shares of common stock per $1,000 principal amount of Convertible Senior Notes (equivalent to an initial conversion price of approximately $5.11 per share of common stock). If the Company undergoes a fundamental change (as defined in the indenture governing the Convertible Senior Notes), holders may require Immunomedics to purchase for cash all or part of the Convertible Senior Notes at a purchase price equal to 100% of the principal amount of the Convertible Senior Notes to be purchased, plus accrued and unpaid interest, if any, to, but excluding, the fundamental change purchase date, subject to certain exceptions. In addition, if certain make-whole fundamental changes (as defined in the indenture governing the Convertible Senior Notes) occur, Immunomedics will, in certain circumstances, increase the conversion rate for any Convertible Note converted in connection with such make-whole fundamental change. The indenture does not limit the amount of debt which may be issued by the Company under the indenture or otherwise, does not contain any financial covenants or restrict the Company from paying dividends, selling or disposing of assets, or issuing or repurchasing its other securities, provided that such event is not deemed to be a fundamental change (as defined in the indenture governing the Convertible Senior Notes). The indenture contains customary terms and covenants and events of default. If an event of default with respect to the Convertible Senior Notes occurs, holders may, upon satisfaction of certain conditions, accelerate the principal amount of the Convertible Senior Notes plus premium, if any, and accrued and unpaid interest, if any. In addition, the principal amount of the Convertible Senior Notes plus premium, if any, and accrued and unpaid interest, if any, will automatically become due and payable in the case of certain types of bankruptcy or insolvency events of default involving the Company. On September 21, 2017, the Company entered into separate, privately negotiated exchange agreements, (the "September 2017 Exchange Agreements") with certain holders of the Convertible Senior Notes. Under the September 2017 Exchange Agreements, such holders agreed to convert an aggregate $80.0 million of Convertible Senior Notes held by them. In total, the Company issued an aggregate 16.8 million shares of common stock in the September 2017 Exchange Agreements. The shares represent an aggregate of 1.1 million shares more than the number of shares into which the exchanged Convertible Senior Notes were convertible under their original terms. As a result of the September 2017 Exchange Agreements, the Company recognized a loss on induced exchanges of debt of $13.0 million representing the fair value of the incremental consideration paid to induce the holders to exchange their Convertible Senior Notes for equity (i.e., 1.1 million shares of common stock), based on the closing market price of the Company's Common Stock on the date of the September 2017 Exchange Agreements. On October 2, 2018, the Company entered into privately negotiated exchange agreements (the "October 2018 Exchange Agreements"), with a limited number of holders of the Convertible Senior Notes. Under the October 2018 Exchange Agreements, the Company exchanged, in a private placement, $12.9 million in aggregate principal amount of the Convertible Senior Notes held by such holders for 2.6 million newly issued shares of the Company's common stock, par value $0.01 per share. As a result of the October 2018 Exchange Agreements, the outstanding aggregate principal amount of the Convertible Senior notes was reduced to $7.1 million in the second quarter of fiscal 2019. Total interest expense for the Convertible Senior Notes for the three months ended September 30, 2018 and 2017 was $0.2 million and $2.6 million, respectively. Included in interest expense was an immaterial amount of amortization of debt issuance costs for the three months ended September 30, 2018, and $1.6 million for the three months ended September 30, 2017 (which included $1.4 million of accelerated amortization of debt issuance costs associated with the $80.0 million exchange of Convertible Senior Notes in September 2017 for the three months ended September 30, 2017).

Debt

Liability related to sale of future royalties:

On January 7, 2018, the Company entered into a funding agreement with RPI Finance Trust, a Delaware statutory trust ("RPI"), under which we sold a portion of our right to receive royalties on potential net sales of the ADC sacituzumab govitecan, in exchange for $175.0 million in cash. Concurrently, we entered into a common stock purchase agreement with RPI through which RPI purchased 4.4 million shares of the Company's common stock for $75.0 million (the "Financing").

The Company concluded that there were two units of accounting in the transaction: (1) the Liability related to the sale of future royalties and (2) the "Financing". We allocated the consideration of $250.0 million on a relative fair value basis to the liability for $182.2 million and the common stock for $67.8 million. We continue to accrete the Liability related to the sale of future royalties using the interest method with an annual interest rate of approximately 19.3%. As of June 30, 2018, we determined the fair value at $202.0 million. During the three months ended September 30, 2018, the Company recognized $9.8 million in interest expense.

Convertible Senior Notes:

In February 2015, the Company issued $100.0 million of Convertible Senior Notes (the "Convertible Senior Notes") (net proceeds of approximately $96.3 million after deducting the initial purchasers’ fees and offering expenses) in a private offering exempt from registration under the Securities Act of 1933, as amended (the “Securities Act”), in reliance upon Rule 144A under the Securities Act. The Convertible Senior Notes will mature on February 15, 2020, unless earlier purchased or converted. The debt issuance costs of approximately $3.7 million, primarily consisting of underwriting, legal and other professional fees, are amortized over the term of the Convertible Senior Notes. The Convertible Senior Notes are senior unsecured obligations of the Company. Interest at 4.75% is payable semiannually on February 15 and August 15 of each year. The effective interest rate on the Convertible Senior Notes was 5.48% for the period from the date of issuance through September 30, 2018.

The Convertible Senior Notes are convertible at the option of holders into approximately 19.6 million shares of common stock at any time prior to the close of business on the day immediately preceding the maturity date. The exchange rate will initially be 195.8336 shares of common stock per $1,000 principal amount of Convertible Senior Notes (equivalent to an initial conversion price of approximately $5.11 per share of common stock).

If the Company undergoes a fundamental change (as defined in the indenture governing the Convertible Senior Notes), holders may require Immunomedics to purchase for cash all or part of the Convertible Senior Notes at a purchase price equal to 100% of the principal amount of the Convertible Senior Notes to be purchased, plus accrued and unpaid interest, if any, to, but excluding, the fundamental change purchase date, subject to certain exceptions. In addition, if certain make-whole fundamental changes (as defined in the indenture governing the Convertible Senior Notes) occur, Immunomedics will, in certain circumstances, increase the conversion rate for any Convertible Note converted in connection with such make-whole fundamental change.

The indenture does not limit the amount of debt which may be issued by the Company under the indenture or otherwise, does not contain any financial covenants or restrict the Company from paying dividends, selling or disposing of assets, or issuing or repurchasing its other securities, provided that such event is not deemed to be a fundamental change (as defined in the indenture governing the Convertible Senior Notes). The indenture contains customary terms and covenants and events of default.

If an event of default with respect to the Convertible Senior Notes occurs, holders may, upon satisfaction of certain conditions, accelerate the principal amount of the Convertible Senior Notes plus premium, if any, and accrued and unpaid interest, if any. In addition, the principal amount of the Convertible Senior Notes plus premium, if any, and accrued and unpaid interest, if any, will automatically become due and payable in the case of certain types of bankruptcy or insolvency events of default involving the Company.

On September 21, 2017, the Company entered into separate, privately negotiated exchange agreements, (the "September 2017 Exchange Agreements") with certain holders of the Convertible Senior Notes. Under the September 2017 Exchange Agreements, such holders agreed to convert an aggregate $80.0 million of Convertible Senior Notes held by them. In total, the Company issued an aggregate 16.8 million shares of common stock in the September 2017 Exchange Agreements. The shares represent an aggregate of 1.1 million shares more than the number of shares into which the exchanged Convertible Senior Notes were convertible under their original terms. As a result of the September 2017 Exchange Agreements, the Company recognized a loss on induced exchanges of debt of $13.0 million representing the fair value of the incremental consideration paid to induce the holders to exchange their Convertible Senior Notes for equity (i.e., 1.1 million shares of common stock), based on the closing market price of the Company's Common Stock on the date of the September 2017 Exchange Agreements.

On October 2, 2018, the Company entered into privately negotiated exchange agreements (the "October 2018 Exchange Agreements"), with a limited number of holders of the Convertible Senior Notes. Under the October 2018 Exchange Agreements, the Company exchanged, in a private placement, $12.9 million in aggregate principal amount of the Convertible Senior Notes held by such holders for 2.6 million newly issued shares of the Company's common stock, par value $0.01 per share.

As a result of the October 2018 Exchange Agreements, the outstanding aggregate principal amount of the Convertible Senior notes was reduced to $7.1 million in the second quarter of fiscal 2019.

Total interest expense for the Convertible Senior Notes for the three months ended September 30, 2018 and 2017 was $0.2 million and $2.6 million, respectively. Included in interest expense was an immaterial amount of amortization of debt issuance costs for the three months ended September 30, 2018, and $1.6 million for the three months ended September 30, 2017 (which included $1.4 million of accelerated amortization of debt issuance costs associated with the $80.0 million exchange of Convertible Senior Notes in September 2017 for the three months ended September 30, 2017).