I checked out MediWiki, Alfresco and Sharepoint. Mediawiki looks cool and Alfresco is definitely cool but a bit more than I need. I didn't realize I could create a wiki on a sharepoint site because all I have is Office 365 Pro Plus. Turns out you can, due to the One Drive integration. I also intend to migrate our on-premise Exchange server to Office 365.
For now I am going to try using Sharepoint. If anyone else has suggestions, please post.
Thanks, everyone.