This user often sends us very detailed feedback.
Mr. Koichi, I heard you were born poor. Could you give me more details on that?
I don’t have enough time to look up the details.
A thing that is detailed and thin is the details. It will help to remember that 細かい also means detailed, which is probably where this meaning is more coming from. Detailed + Detailed = the details.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.