System classes and components

Illuminated Cloud integrates API documentation directly into the editor.  Documentation is provided for virtually all system Apex classes and Visualforce components.
System documentation

Custom classes and components

Illuminated Cloud also shows documentation for custom Apex declarations based their header comments and custom Visualforce components based on their component definitions.
Custom documentation

Visualforce functions and global variables

Illuminated Cloud provides integrated documentation for Visualforce functions and global variables.
Visualforce function and global variable documentation

Method and function parameters

Apex method and Visualforce function parameter information is also always a keystroke away including support for SObject constructor field initializers.
Visualforce function parameter information