CFM 56-7 Min Idle
I also had problems finding an N1idle figure recently after a pilot enquiry.
The best I could come up with at the time was Min Idle for Std day N1-20%.
In flight min idle will vary as a function on min N2, total bleed air, ECS, Anti-ice selection, and minimum compressor static discharge pressure.
The change from min to app idle is done by the fadec, normally as a function of flap position.
I hope that helps?
Cheers !