Wait time is the same as response time or the amount of time it takes to respond to the event the first time.
Idle time is the time after the dispatch has been responded to once a dispatched resource has been removed from the event, but it hasn't been completed yet.
Key Note: When looking at the Dispatch Summary Report, Idle Time is listed, but includes Wait Time. You'll need to subtract Wait time from the Idle time to get the true idle time.
In this example, true Idle Time is 22.