Momentary dimming when you hit the window switches is normal, it's from the sudden increase in current demand for the window motor. If you hit the "up" switch with the window fully up the current is higher because the motor is stalled at the end of the window travel.
Flickering of lights at idle is NOT normal, and indicates a possible problem with the electrical system. You could have a weak battery or alternator. Take some voltage readings at the battery, and check the battery terminals and ground connections.