You you are worried, I suggest multiple locks. No one ever had their bike stolen from using too many locks, and since it is just employees and such, you can probably get away with leaving a U-Lock or 2 attached to the bike rack (cause them things are heavy! At least mine is...I use an OnGuard). The only time I have left my bike outside for more than an hour or so was overnight in Savannah locked to the bike rack outside of my hotel. It was fine there. I would have a Ulock attaching the frame to the bike rack, another attaching the front wheel to the frame, and then a cable lock running through your seat and also around the bike rack. Chances are even if you forgo the 2nd Ulock, if you have more than 1 lock on your bike a potential thief will just move onto an easier target. If you do that, make sure you still lock your front wheel to your frame, or get rid of the quick release skewers in favor of a bolt on. I picked up a set for like 10 bucks that requires a special hex key to take the wheel off. Nothing on my commuter is a quick release.

I am fortunate though that I get to bring my bike inside my work.