Dear
It was better to post this under SRX section ,
the below link will help u to enable IDP logging and post the logs in local file ,
http://kb.juniper.net/InfoCenter/index?page=content&id=KB17291&smlogin=true
if you'd like to send it to external syslog server , so just u need to update the syslog config for IDP as below , assuming you syslog server is 1.1.1.1 , u can even use FQDN , but make sure you configure your dns on SRX
syslog {
host 1.1.1.1 {
any any;
match RT_IDP;
}
}