1. A computer-implemented method for detecting potentially fraudulent cardholder transactions, the method implemented by a fraud detection computer system in communication with a memory, the fraud detection computer system in communication with a payment processor computer device in communication with a plurality of POS devices associated with a plurality of merchants, wherein the payment processor computer device is configured to process payment card transactions, the method comprising: receiving, from the payment processing computer device, historical transaction data including a plurality of payment transactions associated with a first cardholder; identifying a first home location for the first cardholder, the first home location based at least partially on historical transaction data associated with the first cardholder; identifying a first geographic region associated with the first cardholder based on the first home location; identifying an expected range of travel relative to the first home location for the first cardholder when making a typical financial transaction in at least one merchant category based on the first geographic region; receiving, from the payment processing computer device, transaction data associated with a first financial transaction initiated by the first cardholder with a first merchant of the plurality of merchants, the transaction data including merchant data and cardholder data, the first merchant being included within the at least one merchant category; retrieving the first home location based on the cardholder data and a merchant location for the first merchant based on the merchant data; calculating, by the fraud detection computer system, a distance of travel between the first merchant location and the first home location; comparing the calculated distance of travel to the expected range of travel for the at least one merchant category and the first geographic region; and flagging the first financial transaction as potentially fraudulent upon determining that the calculated distance of travel exceeds the expected range of travel.