I don't know about documentation -- you could check the recent version of the whitepaper here https://steem.io/SteemWhitePaper.pdf
The 50% split is pretty confusing right now because SBD is trading very high; my article here explains a little: https://steemit.com/sbd/@biophil/go-home-sbd-you-re-drunk-how-to-maximize-your-author-rewards