Commitments and Contingencies - Office Space in Munich, Germany (Details) - USD ($)	12 Months Ended
Feb. 28, 2020	Feb. 28, 2019	Feb. 28, 2018
Operating leases
Lease rent per month	$ 14,700	$ 14,200	$ 13,800

Represents the amount of payments that the lessee is obligated to make or can be required to make monthly in connection with a property under the terms of an agreement classified as an operating lease, excluding contingent rentals and a guarantee by the lessee of the lessor's debt and the lessee's obligation to pay (apart from the rental payments) executory costs such as insurance, maintenance, and taxes.

No definition available.

Name:	ontx_OperatingLeasesRentExpenseMinimumRentalsPerMonth
Namespace Prefix:	ontx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration