What wrong did I do by demanding for my man's bank account details? Please help me somebody!!!!

I think i'm losing this precious man of mine, we have been so good together and I have had no reason to doubt him, but recently I read a relationship book and the author stated categorically that the reason her relationship has worked is because she knows every detail about her man and that info includes his bank account details. So I took that advice hook, line and sinker and I decided to ask my man for his bank account and the monies he has and the response I got was so unexpected, he flared up and I couldn't believe he'd yell at me in that way. Right now, he's not in speaking terms with me, he recoiled and i'm not comfortable with his new attitude, would I have left him alone? He acts like I bruised his ego.
Dear Girls, please help me, why would he hide his bank details from me? Is he hiding something from me?
I need my man back please help me.