IntelliJ IDEA 2017.3.2 (Ultimate Edition)
Build #IU-173.4127.27, built on December 25, 2017
JRE: 1.8.0_152-release-1024-b8 x86_64
JVM: OpenJDK 64-Bit Server VM by JetBrains s.r.o
Mac OS X 10.13.2
After upgrade to latest 2017.3, IntelliJ frequently spikes to 600+ CPU with no obvious activity. I think this typically happens when the editor is brought to focus after a longer period of being in the background, but I haven't isolated a good consistent repro. At that CPU usage, the software is essentially unusable for a few minutes. Other engineers on our codebase have reported similar symptoms.
I'm not sure what other info to provide; we are on Scala-based projects with a fairly large codebase. latest Scala plugin. The above change occurred on the same codebase where older versions of IDEA did not have this problems.