Surprisingly, the word "idle" means that the CPU is idle.
It's only busy when it isn't idle, so the actual CPU load is 100% - 71.64% or 28.36%.
Pinging TO a switch is a very low priority process compared to pinging THROUGH a switch. Network equipment is optimized to pass traffic through the device and not to terminate traffic. It sounds to me as if it's working properly.
Jayh, After looking at that again and you pointing that out idle means idle, my eyes were so drawn to the 71.64% i never considered it that way thank you for clarifying and for looking at my config.