Outputting Relation after Select - Eloquent Laravel

I have a laravel application and I've created a relationship between one table and another.

The relationship is a hasOne on my OrderDetail Model

public function customer()
{
    return $this->hasOne('App\Customer', 'CU_ACC_CODE', 'OD_ACCOUNT');
}

I'm performing a query on my OrderDetail

    $orders = OrderDetail::where('OD_ENTRY_TYPE','S')
                        ->where('OD_STATUS','0')
                        ->where('OD_QTYRESERVED','<>','0')
                        ->select(
                            DB::raw('CASE WHEN SUM(OD_QTYORD)=SUM(OD_QTYRESERVED)THEN 1 ELSE 0 END AS FullAllocated'),
                            'OD_ORDER_NUMBER',
                            DB::raw('SUM(OD_QTYORD) AS Ordered'),
                            DB::raw('SUM(OD_QTYRESERVED) AS Allocated')
                            )
                        ->with(['customer' => function($query) {
                            $query->select('CUNAME');
                        }])
                        ->groupBy('OD_ORDER_NUMBER')->get();

    dd($orders);

And I'm not getting anything back from the customer relation?

The result is null, but I know the relationship is indeed working and there is a link between the two.

Any ideas?

via Chebli Mohamed