Debt - Deferred Revenue, By Arrangement (Details) - Funding agreement - RPI Finance Trust $ in Millions	3 Months Ended
Sep. 30, 2018 USD ($)
Debt Instrument [Roll Forward]
Liability related to sale of future royalties	$ 202.0
Interest expense recognized	$ 9.8

Non Cash Interest Expense Related To Sale Of Future Royalties

No definition available.

Name:	immu_NonCashInterestExpenseRelatedToSaleOfFutureRoyalties
Namespace Prefix:	immu_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration