That is not what the description on the front page or several internal pages say. The maximum voltage is 80 V *only* if the other pin is less than 18 V below it. You cannot have one input pin at 80 V and the other at 60 V, or 18 V, or 0 V. If one of the pins is at 0 V, the maximum voltage on the other pin is 18 V. This is the differential input voltage spec. The part is not a general purpose opamp; it is purpose-built for one application, and can be extended to a few more.
ak