We use Direct Line ("Linea Directa" here in Spain) . It's fully, legally insured as a holiday let, with liability and damage cover. We've had great service from them so far, and the prices are very competitive.
But just as an add-on suggestion, as a new host, please be sure to peruse the many advices given about hosting here. It's not really the doddle Airbnb likes to imply that it is. And there's a lot of subtlety that makes a big difference.
Just stay in top of it, vet your guests carefully, focus on quality over quantity (spend your energy on delivering a quality product, and the money will ultimately follow), price it intelligently (that doesn't include Airbnb price suggestions, which are always much lower than you can consistently get), and don't expect or depend on much help from Airbnb, and you should be fine.
Welcome to hosting, and wishing you all the best with that! It can be pretty rewarding, even if occasionally frustrating.
