Which mind mapping tool works best for planning large product ideas?

I'm one of those people who still starts every big project with pen and paper. The problem is that once the idea grows beyond a page or two, everything becomes impossible to organize. I end up redrawing the same mind map multiple times because priorities change, new features get added and different people contribute ideas. I'd like something that starts as simple brainstorming but can eventually become something the whole team can build on instead of staying in my notebook.