I'm using IntelliJ IDEA on Arch Linux with KDE. OpenJDK version is 1.7.0_40.
Whole IDE fonts (includes code editor) are rendered without any antialiasing and font smoothing. I set in idea.properties file idea.use.default.antialiasing.in.editor to true, and added in _JAVA_OPTIONS variable -Dawt.useSystemAAFontSettings=on -Dswing.aatext=true without any effect.
What else I can try to enable font smoothing?

Take a look here. I remember having the same problem when running IDEA, but after adding the line mentioned in the wiki the problem goes away.
export _JAVA_OPTIONS='-Dawt.useSystemAAFontSettings=setting'wheresettingmay beofforfalseordefault– No anti-aliasingon– Full anti-aliasinggasp– Use the font's built-in hinting instructionslcdorlcd_hrgb– Anti-aliasing tuned for many popular LCD monitorslcd_hbgr– Alternative LCD monitor settinglcd_vrgb– Alternative LCD monitor settinglcd_vbgr– Alternative LCD monitor setting