Highmaps border color of region

I am using Highmaps in one of my web based application. Until now it was easy to modify it according to my use case but now i need to changes the border color of the region and i am unable to do it.

Code i have tried but failed:

chart: {
                plotBorderColor: '#ffffff',
                borderColor: "#ffffff",
       }

See attached image what i want to achieve

Want to change the outline color to white

http://jsfiddle.net/qLen614m/

You can use the stroke attribute of the path element:

path {
    stroke: white;
}