Not seeing anything easy that I agreed with on the web, I went to Github and created a QND (Quick -n- Dirty) tool with Boostrap v.3.4.1 and jQuery to document your API. It's super easy to use if you know HTML. If you know Bootstrap (any version), then you might be able to accomplish some tasks sooner or better.
The tool provides a language chooser that you can customize in the upper right, a logo that you can swap, a title of "API Documentation" that you can change, a sidebar of API items (broke out by category title, then API links and sub links), a middle that contains tables and info about your API, and a ride sidebar that shows examples and URLs with automatic code formatting.
Try it out here: https://github.com/volomike/bootdox
This is an early, yet decent beta, and I'm sure there's some room for improvement. Feel free to fork it at Github, make some changes, and then I can integrate your changes.