Unable to get property 'appendChild' of undefined or null reference error in IE 11

[Costa Basil]

This sample bombs in IE11 when I hover the mouse over a circle: http://bl.ocks.org/emeeks/ea5760799fce0b3a2e7c.

function highlightRegion(d,i) {
 var teamColor = d3.rgb("pink")
 d3.select(this).select("text").classed("highlight", true).attr("y", 10)
 d3.selectAll("g.overallG").select("circle").style("fill", function(p) {return p.region == d.region ? teamColor.darker(.75) : teamColor.brighter(.5)})
 this.parentElement.appendChild(this);

}

Is there a workaround to get it working in IE 11?

Thanks