intellij, The source preview is slowly when my mouse point is over right's scroll in IntelliJ SDK

It's a useful feature for quickly showing preview mini source code.


But I don't want to work this function. My Intellij Program was slowly.

Do you know how to cancel it? I can't find disable this feature Because I don't know what's name of feature.

Do you help me to do disable feature or what's name or Performance tuning?

**My Environment**
MACSierra 10.12.6
Intellij IDEA 15.0 ULTIMATE, Build #IU-143.381
JRE : 1.8.0