What should we do if we show a 0% cpu idl on top?
Identify from top itself that which is the process is hogging CPU resources.
Top's default behavior should list the culprit process as the first process
The true question is for how long (it could be a temporary normal situation...) and how is the cpu usage? more than 75% user would mean all is fine more than 60% system means you need to investigate...
If top shows several cpus all at 100% for a sustained period of time there is a capacity problem or some rogue software. If you only have one cpu it will show 100% whenever it is used (even by the program top itself).
What is the scale of this server?
I suppose that these should be the only temporary peaks. Try vmstat -5 and collect some data so we have possibility to clarify if this is the really pain of your server. Via prstat -s cpu you can clarify which process is so cpu demanding.