The "classic" mode of the Virus TI only produces a single oscillator signal per oscillator, hence there is no "detune" for this. The "detune" parameter is available in Hypersaw since this mode allows you to create more than a single Oscillator signal which you then can detune against each other.
The only option or better "workaround" in "classic" mode is to use the UNISON mode and then detune the UNISON voices against each other, however this also will eat up voices very quickly at high UNISON settings.
