I offer my own experience as a co-op unit owner. I do have coop-specific insurance available to me here.
There are three main aspects to the insurance:
1) Liability (property damage and bodily injury; sometimes personal injury as well);
2) Contents; and
3) Rebuilding (not always called that).
What would happen if a tragedy struck your building and it was completely destroyed; say, by the fire department making a firebreak against a huge municipal conflagration? The whole building and everything in it is reduced to ashes and blown away by the wind.
Typically a co-op will carry enough insurance to rebuild, to current code, with the same units at the same size, with all behind-the-walls plumbing; electrical; gas; whatever. You will have to replace the interior: kitchen; bathroom; ceiling lights; interior walls & doors; electrical outlets; probably fuse box; everything.
You need enough insurance to restore your unit from bare drywall.
Sometimes insurance will help with alternate living expenses while the building is being reconstructed. Some policies also offer limited coverage against increased assessments to cover building damage. I'm sure there are more clauses in more policies in more buildings in more states than I am familiar with.
Maybe you could try to find out (your insurance agent may be a source, if not a completely unbiased one) the cost per square foot to completely renovate (which is much the same thing).
Does that help?