The calculated distance (air line) between Šentilj v Slov. Goricah and Idrija is approximately 90 miles respectively 145 kilometers.
By car or train, the actual journey to Idrija is certainly longer, as only the direct route (as the crow flies) between Šentilj v Slov. Goricah and Idrija has been calculated here.
Air line (approximately)
145 kilometers
78 nautical miles