Note 9 - Subsequent Events (Details Textual)	May 02, 2017	May 01, 2017
Patency-2 Trial [Member] \| Subsequent Event [Member]
Planned Enrollment, Number of Patients	600	500

Represents the number of patients that plan to enroll in an experimental trial.

No definition available.

Name:	prto_PlannedEnrollmentNumberOfPatients
Namespace Prefix:	prto_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant