Convertible Senior Notes - Narratives (Details) $ / shares in Units, shares in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Feb. 28, 2015 USD ($) $ / shares shares	Mar. 31, 2016 USD ($)	Mar. 31, 2015 USD ($)	Mar. 31, 2016 USD ($)	Mar. 31, 2015 USD ($)
Debt Instrument [Line Items]
Amortization of debt issuance costs				$ 547,366	$ 99,337
4.75% Convertible Senior Notes Due 2020 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount	$ 100,000,000
Net proceeds from debt	96,300,000
Debt issuance costs	$ 3,700,000
Debt instrument, maturity date				Feb. 15, 2020
Frequency of interest payments				Interest at 4.75% is payable semiannually on February 15 and August 15
Debt instrument, stated percentage	4.75%
Debt instrument, effective interest rate		5.48%		5.48%
Number of shares issuable under conversion of debt | shares	19.6
Debt conversion ratio	195.8336
Conversion price of debt | $ / shares	$ 5.11
Convertible Senior Notes, terms of conversion				The conversion 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 Immunomedics common stock)
Percentage of principal amount redeemable	100.00%
Interest expense		$ 1,400,000	$ 700,000	$ 4,100,000	700,000
Amortization of debt issuance costs		$ 200,000	$ 100,000	$ 500,000	$ 100,000