Currently, the time entry detail report does not calculate the cost for non-billable time entries. If a non-billable time entry is captured, the cost on the time entry report for that entry is 0.00.
Please update the cost on the time entry detail to calculate for non-billable projects as well.
Users have the ability to filter the time entry detail report to view only billable items, if that is the required view, but allowing the calculation to run will allow organisations to keep track of their internal staff cost as well.