Inspect HTTPS Traffic With IDS/IPS

Is it possible to perform IDS/IPS on traffic that is SSL encrypted? I am setting up a secure Apache reverse proxy with a CISO ASA and a Citrix Netscalers in front of the reverse proxy.

Here's a "diagram" of my environment:
Client --SSL--> Firewall --> Load Balancer --> Reverse Proxy [url] --SSL--> Portal Server [url]

I am trying to find a way to add additional security before traffic reaches the Portal Server. Also is it possible to add mod_security to the reverse proxy, since the traffic to the backend server is encrypted?