I've been wanting to get started on Luther for a while, actually! I watched the first season of the Wire and I really like Idris Elba. After this recommendation I really want to start watching it finally.
You won't regret it. Or maybe you will - it gets pretty brutal in places. But hopefully not! I haven't seen The Wire, but I've heard good things. It might be a shock to hear him with an English accent, I've heard people say that they didn't realize he wasn't American after watching The Wire.
I liked the Wire a lot. I feel like it portrays the cop world extremely authentically. It starts off slow but it's because they have to introduce the cast of characters and set it up well. At some point they pick up the pace and it gets more complex and interesting from there. And yes, Idris Elba does have a great American accent, but I've seen trailers for Luther and I think I'll manage to get used to his Britishness.