Animation Types: Humanoid vs. Generic breaking my rig

Trying to get an idle and walk animation onto a character to test my rig. I've exported two FBX files that appear to run completely fine when I import them into Maya and Motionbuilder, but when I import the Idle animation into Unity, the eyes stop working (even if I delete, rebuild, and reexport them.)

I know it must be a Unity problem, because when I set the animation type to "Humanoid" mode, the Idle animation works perfectly, eyes included. But once I leave "Generic" mode, the Walk animation stops working and explodes on me. Before I start sharing FBX files, I just need to know if there's something specific that Unity is looking for when I build a rig? Do the different animation types struggle with naming conventions or joint hierarchies?