The pilot reported to the Federal Aviation Administration Inspector that he was working with the land owner to conduct cattle herding with the helicopter. He landed in the field and got out to speak with the land owner about the flight. The pilot left the helicopter at idle power when he exited. While speaking to the land owner, the collective/throttle increased and the helicopter rocked back on the tail, separating the tail rotor. The main rotor blades were then damaged when the helicopter settled back down.The helicopter received substantial damage to the tail rotor and main rotor blades. Robinson Helicopter's issued Safety Notice SN-17 in November 1984, revised June 1994, which stated: NEVER EXIT HELECOPTER WITH ENGINE RUNNING Several accidents have occurred when pilots momentarily left their helicopters unattended with the engine running and rotors turning. The collective can creep up, increasing both pitch and throttle, allowing the helicopter to lift off or roll out of control.