"In intimate details" refers to very personal or private information about someone or something, which is often known only by a few people or not shared openly with others. Full definition
Maybe you or your partner won't feel comfortable sharing intimate details of your sex life in front of a third person but, believe me, there is nothing to worry about. (marriage.com)
He hasn't had to have a lengthy conversation with the woman who shares intimate details about the lives of her cats. (relevantmagazine.com)
Stay open - minded and don't be afraid to share intimate details of your life before you met him. (cupidspulse.com)