Documenting is hard, often because there's no good place to keep documentation handy. I prefer ER diagrams, but you really need some snippets from Word or someplace handy to note what columns mean. And it should be something that links together related columns.

I've tried Word, Excel, Visio, ER/Studio, ErWin, HTML and more over the years. The only thing that's ever worked well for documenting the database is my brain loaded with experience in working with the tables.