How to detect if player is idle?

I've looked through Google and the DevForums, but I can't seem to find anything that works, here is what I have so far.

local running
local humanoid = game.Players.LocalPlayer.Character:WaitForChild("Humanoid")
humanoid.Running:connect(function(speed) -- return value; speed of the running
if speed > 0 then running = true
    script.Parent:WaitForChild("1"):TweenPosition(UDim2.new(0.5, 0, 0.545, 0), "Out", "Linear", 0.3, false)
    script.Parent:WaitForChild("2"):TweenPosition(UDim2.new(0.5, 0, 0.465, 0), "Out", "Linear", 0.3, false)
    script.Parent:WaitForChild("3"):TweenPosition(UDim2.new(0.49, 0, 0.505, 0), "Out", "Linear", 0.3, false)
    script.Parent:WaitForChild("4"):TweenPosition(UDim2.new(0.51, 0, 0.505, 0), "Out", "Linear", 0.3, false)
    print(speed)
    end
end)

Basically, it's a dynamic crosshair. I have got this to work with loops, but they prevent seperate edits to the crosshair as it is constantly tweening it. Thanks in advance.

(also I didnt write that code apart from the tweening part, I'm bad with this kind of stuff)