The input bias current is typically 5 pA for input voltages between V+ and GND. The comparator inputs are protected from reverse voltage by the internal ESD diodes connected to GND. As the input voltage goes under GND, or above the input Absolute Maximum ratings the protection diodes become forward biased and begin to conduct causing the input bias current to increase exponentially. Input bias current typically doubles for each 10°C temperature increase.
If the inputs are to be connected to a low impedance source, such as a power supply or buffered reference line, TI recommends adding a current-limiting resistor in series with the input to limit any transient currents should the clamps conduct. The current should be limited 10 mA or less. This series resistance can be part of any resistive input dividers or networks.