I believe the OP is using Docco.js (which has been ported to many languages, e.g. Rocco for Ruby, Shocco for Shell, Pycco for Python, Gocco for Go, etc.)

http://jashkenas.github.io/docco/

There's different ways to configure the output and layout...the Docco homepage uses a single-column format, whereas the OP uses the double-column format.