Filtering a field with value iterations

I need to filter a field containing contract numbers.  The format of the contract numbers is something like this -- there is a main part and if there are variations, a decimal with another group of numbers follow.  Example, 8596 is contract number and variation is 8596.1 and 8596.2.  In my report, I only want to capture those that do not contain decimals. How do I filter them? Thanks.