When IDEA is used on a system with IBus is installed and running keyboard input sometimes became blocked by IBus daemon. Event Dispatching Thread is active. All other events are delivered in order - i.e. it is possible to select text or call menu actions by a mouse.
Solution:
Either upgrade IBus to version 1.5.11 or add "export IBUS_ENABLE_SYNC_MODE=1" to your ~/.profile, then restart a session.
Alternatively, you can turn off IBus at System Settings | Language Support | Keyboard input method.
IDEA 15 will show a warning if an incompatible version of IBus is in use.
checkout this link for detals https://youtrack.jetbrains.com/issue/IDEA-78860
