Basically, you had to have the project designed, before pitching it. After that, it had to go through a lot of folks, flinging poo at it (They called these meetings "Design Review" meetings, or "DRs").
It certainly resulted in relatively successful outcomes (and I saw failures, where managers let stuff pass without that level of detail), but I think it also killed a lot of good stuff. Some ideas are worth approaching, even if the approach has not been fully mapped-out.
I'm a huge fan of "Evolutionary Design"[0-1]. It has served me well, but is not for the faint of heart (or the inexperienced). If you don't have a lot of experience (as opposed to intelligence and/or education), then I do not recommend this approach.
I am also a fan of "biting off more than you can chew"[2]. Again, I would only recommend this for experienced people, if it is for shipping projects.
If not for shipping projects, then go for it. Knock yourself out.
[0] https://littlegreenviper.com/miscellany/forensic-design-docu...
[1] https://littlegreenviper.com/miscellany/evolutionary-design-...
[2] https://littlegreenviper.com/miscellany/thats-not-what-ships...
That said, even a very rough outline of an idea should be subjected to an appropriate amount of high-level criticism.
Caveat: One may have to reframe the problem to really solve it http://www.azarask.in/blog/post/the-wrong-problem/ | https://archive.is/uLlkx