A buzzword in the AEC community with a rather fuzzy definition. Basically, it’s the idea of keeping large construction projects on track and within budget by getting all disciplines — construction, design and architecture, MEP, etc. — to think about how their piece fits into, interacts with and affects the overall project rather than working in isolation, risking conflict and error. The Wikipedia entry for IDP says much more than we can here and will surely grow and refine over time, so we’re going to refer you there.