Align iframe to the center

Question

I am trying to align iframe to the center but for some reason it is showing from the left side whereas I want the iframe and it's elements to be on the center. I used the iframe inside a div but it's not working and showing from the left side. I want it to be dynamically aligned. Can anyone help?

<div id="modalReportView" class="modal fade" role="dialog">
    <div class="modal-dialog modal-report">
        <div class="modal-content">
            <div class="modal-header">
                <button type="button" class="close" data-dismiss="modal">&times;</button>
                <h4 class="modal-title modalhead" style="">Report Viewer</h4>
            </div>
            <div id="content" class="modal-body" style="padding: 15px 30px 30px 30px; background: #808080; overflow-x: hidden;">
                <iframe id="reportIframe" scrolling="no" style="width: 100%; height: 910px; border: none;">
                </iframe>
            </div>
            <div class="modal-footer">
                <div class="col-md-12">
                    <a href="#" class="btn btn-sm btn-danger btn-block" id="closeModalButton" data-dismiss="modal"><b><i class="glyphicon glyphicon-remove"></i> Cancel</b></a>
                </div>
            </div>
        </div>
    </div>
</div>
-----------JS code-------------------
function ViewReportDetails(_dbModel) {
$("#reportIframe").attr("src", "");

var ItemModuleFrom = jQuery.grep(moduleWiseReportClass, function (p, i) {
    return (p.Module == _dbModel.ModuleFrom);
});

_dbModel.ReportHelperClass = ItemModuleFrom[0].HelperClass;

var reportUrl = "/ReportsManagement/ReportView/ReportViewer?json=" + encodeURIComponent(JSON.stringify(_dbModel)); // for rdlc report
console.log(reportUrl);

////for rdlc report
$("#loading").show();
if ($("#reportIframe")[0].contentWindow.document.readyState === 'complete') {
    $("#reportIframe")
        .attr("src", reportUrl)
        .on('load', function () {
            $("#loading").hide();
            $("#modalReportView").modal('show');
        });
}
$("#closeModalButton").on('click', function (e) {
    $("#modalReportView").toggle();
});

}