70C while idling is pretty bad.
In all likelihood the thermal paste has dried up. You will want to clean off the thermal paste from both CPU and the heatsink as soon as possible. Stressing a CPU (like playing games) can cause temps to rise by 25C so when playing games your CPU might be running at 95C or higher.
I recommend Arctic Silver 5 or IC Diamond thermal compound. Excessive heat can cause the CPU to fail.