Schedule of time over which an entity anticipates to receive utility from its property, plant and equipment (that is, the periods of time over which an entity allocates the initial cost of its property, plant and equipment).

No definition available.

Name:	prto_PropertyPlantAndEquipmentUsefulLivesTableTextBlock
Namespace Prefix:	prto_
Data Type:	nonnum:textBlockItemType
Balance Type:	na
Period Type:	duration