Help with String to Array (maybe regEx?)

[kill_robot_kill]

I need some help figuring out how to create an array from a string.
The string will look something like this:

Main Idea
-Idea 1
--Idea 1 sub point 1
-Idea 2
--Idea 2 sub point 1
---Idea 2 sub point 1 subsub 1
---Idea 2 sub point 1 subsub 2
--Idea 2 sub point 2
-Idea 3

Each “-” indicates a child relationship or ‘Sub’. Each child can have any number of children which can have any number of children.

thanks!