Our cities are literally infested with drug addicts, these people need money even if it is just a couple of bucks. Myself I wouldn't bother leaving something I care about at a train station but... if I had to I would get a beater specifically for it. Ideally it would be a dumpster bike with only enough maintenence to make it rideable. A couple of heafty locks, but I wouldn't worry to much about them: they are only to keep the honest people honest. When parking your bike be sure to take all attatchments with you.

I park mine on a college campus and my criteria for location are in order of most important to least: secure lockage, cover from rain, bikes worth more than mine, bikes not as well locked as mine, observable from my destination, no car traffic, lots of foot traffic

I would never leave a valuable or semi-valuable bike out in the open at night. Never underestimate the tornado of destruction that is a bored teenager. They won't try to steal your bike, they will just destroy what they can (tacoing the rear wheel seems popular).

I would avoid using your renters insurance to cover a small claim like a bike, you'll regret it when you go to get homeowners insurance and they give you a higher rate because of a claim history.