Actually, it isn't about impedance at all. It is about the voltage swing available at the output of the source device. At this point, audio is merely AC voltage operating at a variety of frequencies.
You can always go from a lower impedance source to a higher impedance load with no problem, assuming you have adequate output voltage coming from the source. To drive a normal high impedance line level input, you usually need anywhere from 0.5 to 1 volt. It is nice to have a bit more available, just for headroom. It is usually no problem to take the headphone output of most modern devices to drive a line level input. It is possible that the Insignia does not have sufficient output level, but I sort of doubt that.