AD8306 input signal level spec's

In perusing the AD8306 datasheet, I see we've listed the max input level (single ended) at +20dBm.  If my conversions are correct, this allows for a +/- 3.16v signal to be applied to the part.  Wouldn't this condition cause a signal below ground to be applied to the input?  Does this not violate our 'standard' max ratings that input signals be within the supply rails?