Floating and high impedance state can never be active levels in any kind of circuit, because floating means, that there's no path to shunt interference to ground. A floating place is extremely sensitive to noise, leakage currents and charge injections from switchings. It's so sensitive, that a good developer avoids floating at all and always adds pull-ups or pull-downs.

Another disadvantage is, that a floating potential at the input of a CMOS-inverter can dramatically increase its power consumption.

And, finally, there is a conceptual mistake: How to detect floating at all? By the help of a potential? Well, each toggling from low to high or vice versa means a brief "floating" then...

Kai Klaas