The CPU idle temperature primarly depends on a few things:
Ambient Temperature - Room Temperature, basically.
The number of fans that are connected to your case blowing air in and out.
What CPU cooler you have/Thermal Paste.
Idle temperature for me is around 40c in most cases, as I'm in a really small room so it heats up quickly.
34-35c is completely normal for idle temperatures, it is generally 5-10C~ above your ambient temperature.
http://www.tomshardware.co.uk/forum/id-1800828/intel-temperature-guide.html