We've implemented plain old MediaWiki in our division. It serves as a document and guidance distribution point to the wider corporate public, as well as an scratch pad for internal procedures and process. Due to the general lack of fine-grained access control and segmentation, we stood up two instances: one for the "public" site without authentication for read-only access (and mediawiki accounts for division members…
We use MediaWiki, it works for us just fine
We have a backing internal discussion board for people to discuss training/presales/help and the like which is good for identifying gaps in the doco as well.