1. A computer implemented method for maintaining a custodian directory, the method comprising: extracting, by a processor, identity information from a document, the identity information including a custodian identity attribute; determining that the identity information is associated with a first custodian; determining whether the first custodian is in a custodian directory by searching for the custodian identity attribute in the custodian directory; creating, in response to determining that the first custodian is not in the custodian directory, a new entry for the first custodian in the custodian directory, the new entry including the identity information; updating, in response to determining that the first custodian is in the custodian directory, an entry for the first custodian in the custodian directory using the extracted identity information; and carrying out a cleanup of the custodian directory by: identifying two or more entries in the custodian directory that have at least one matching custodian identity attribute; determining a weighting factor for each field in the custodian directory, wherein the weighting factor for each respective field is based on a likelihood that the custodian identity attribute for the respective field is unique to a single custodian; generating a relationship score for the two or more entries by comparing the identity information in the two or more entries and using the weighting factors, the relationship score being a numeric score that indicates a level of similarity between the two or more entries; determining that the relationship score exceeds a confidence threshold; determining, based on the relationship score exceeding the confidence threshold, that all of the two or more entries in the custodian directory relate to a particular custodian; and merging, in response to determining that all of the two or more entries relate to the particular custodian, the two or more entries in the custodian directory.