For me, it's a combination of both. However, I wouldn't exactly call my planning
meticulous because my brain would not let me usually sit to detail out a idea. Once I have one, I find that figuring out the detail becomes easier once I start to write; as long as I keep my idea in mind, then arriving at that point eventually takes place

However, during the course of the writing, new ideas spring up and that's when I write them down. Maybe they'll be useful to the current storyline? Maybe they'll be used for another? Who knows!