As-built Design & Detailed Design - How do they vary?

Anyway, this is likely different in separate parts of the world. In Australia a detailed design is made prior to implementation. It's after a high level or macro type design, but before implementation.

An as built is, as it's name suggests, a document 'as it is built' - after implementation. The as built document can only be written after implementation

As-built designs are created to sync with the existing designs after construction while detailed designs are done prior to the construction phase so that they are designed to accuracy.

High Level Design vs Detailed Design vs As-built Documentation High Level Design (HLD) - Translates business requirements into a complete architecture design decisions for all key components of the project Detailed Design Document (DDD) - Describes the architecture of each of the key components.