Your going to have to measure that one for yourself for your vehicle.
It will vary a lot depending on battery age and condition, the temperature of the alternator and air around it and what accessories may be running.
Generally, the alternator is "geared" to run just fast enough to handle typical operating loads at idle like engine electronics, lights, fan and perhaps A/C without drawing the battery down..
Just because it may be a "220A" alternator, doe not mean it can and will produce all 220A at idle OR for LONG PERIODS OF TIME..
It is intended to provide short intermittent bursts of current to cover spikes like your power windows and such. We are talking seconds to a few minutes, not hrs of heavy use.
