I must run IntelliJ IDEA on Linux, but OS X is my OS of choice. After trying various setups involving X Windows, VNC, x2vnc, and Synergy, I've settled on running IDEA from my Linux box under X11 for OS X. In other words, IDEA runs on the Linux box but displays in OS X. For some reason, the Alt key did not work out of the box (which becomes an issue when I try to select a menu or hit "Alt+Enter" to import a class). I fixed the issue by creating .Xmodmap in my home directory on my Mac:

  keycode 66 = Alt_L
  clear Mod1
  add Mod1 = Alt_L Alt_R