Depends on the specific topic. If it's just "sex talk" like something funny, etc. I talk to my two best friends (not at the same time). And only if I happen to be talking to them. I don't call them up to chat about it.
And if it's something serious, or kind of TMI, I talk to one friend because we're all about TMI, especially since she had kids (People with kids are ALL ABOUT TMI). She tells me her stuff, I tell her mine. No judgement of course.
I am pretty open with my sister and I have a friend that I can speak about ANYTHING with but other then I will skim over details. The only person I think I would go into details with lives in another pronice and I don see often. :(