Cannot pass "IEnumerable>" from view to controller?

Question

MCV5 My Razor model type is: IOrderedEnumerable

I cannot figure out how to post back to the controller. If I use a regular ViewModel class it works fine, but as I have a Header/Detail on my Razor page, when I try to post back, as IOrderedEnumerable, an error is instantly generated and I cannot figure out how to post back...

My ViewModel:

public class DocumentViewModel
{
    [Display(Name = "Repostitory")]
    public string Repository { get; set; }
    public int DocId { get; set; }
    [Display(Name = "Statement Date")]
    public DateTime DocDate { get; set; }

    [Display(Name = "Account Number")]
    public string AcctNum {get;set;}
    public string FND { get; set; }
    public string strURL { get; set; }
    public int UserID { get; set; }

}

My code to populate the header/detail of the view model:

{
    ViewBag.dropdownMonths = new SelectList(db.vDDLMonths.ToList(), "codeID", "codeText","0");
    ViewBag.dropdownYears = new SelectList(db.vDDLYears.ToList(), "codeID", "codeText","2016");
    ViewBag.UserId = Convert.ToString(model.userID);
    //Generate Querystring 
    //Pull Account List
    string strQSAccountList = (from u in db.vUserParticipantQS
                               where u.userID == model.userID
                               select u.AccountNumbersList).FirstOrDefault();

    string strQueryString = BuildQueryString("List");
    string strMonth = "0";
    string strYear = "2016";
    string strStartDate = strYear;
    string strEndDate = strYear;

    int intMonth = 0;

    if (int.TryParse(strMonth, out intMonth))
    {
        if (intMonth > 0)
        {
            strStartDate += strMonth;
            strEndDate = strStartDate;
        }
        else
        {
            strStartDate += "01";
            strEndDate += "12";
        }
    }
    //Pull Months  based on 
    strQueryString = strQueryString + "&BYM=" + strStartDate + "&EYM=" + strEndDate + "&A=" + strQSAccountList;

    string newURL = BuildEncryptedURLRequest(strQueryString);
    List<DocumentViewModel> docs = new List<DocumentViewModel>();
    docs = XMLBuild.CreateXML(newURL, model.userID);

    //Group results (for display in Razor view)
    var queryAcct =
        from doc in docs
        group doc by doc.AcctNum into AcctGroup
        orderby AcctGroup.Key
        select AcctGroup;

    return View("~/Views/Statements/Docs.cshtml", queryAcct);// This passes a type of IOrderedEnumerable<IGrouping<string, AodNetIntegration.Models.DocumentViewModel>>

}


public static List<DocumentViewModel> CreateXML(string newURL,  int UserID)
{
    XmlDocument docXML = new XmlDocument();
    docXML.Load(newURL);

    XmlNodeList nodes = docXML.DocumentElement.SelectNodes("/page/ALCHEMY/DOC");

    List<DocumentViewModel> docs = new List<DocumentViewModel>();
    int Id = 0;
    DateTime dt;
    string qs = "";
    string url = "";
    string docDate="";
    foreach (XmlNode node in nodes)
    {
        DocumentViewModel doc = new DocumentViewModel();

        doc.Repository = node.SelectSingleNode("REPOSITORY").InnerText;
        if (int.TryParse(node.SelectSingleNode("DOC_ID").InnerText, out Id))
            doc.DocId = Id;
        if (DateTime.TryParse(node.SelectSingleNode("DOC_DATE").InnerText, out dt))
        {
            doc.DocDate = dt;
            docDate = dt.ToString("MM/dd/yyyy");
        }

        doc.AcctNum = node.SelectSingleNode("A").InnerText; //node.Attributes["id"].Value;
        doc.FND = node.SelectSingleNode("FND").InnerText;
        doc.UserID = UserID;
        //create direct link for each statement
        qs = BuildQueryString("Document") + "&A=" + doc.AcctNum + "&DTE=" + docDate; //A=ACG473&DTE=07/31/2016;
        url = BuildEncryptedURLRequest(qs);
        doc.strURL = url;
        docs.Add(doc);
    }

    Debug.WriteLine("Total docs: " + docs.Count);
    docs.OrderBy(o => o.AcctNum)
        .ThenBy(o => o.DocDate);

    List<DocumentViewModel> docAccts = new List<DocumentViewModel>();

    return docs;
}

Model code:

    @model IOrderedEnumerable<IGrouping<string, AodNetIntegration.Models.DocumentViewModel>>

    @using (Html.BeginForm("GetStatement", "Statements", new { ReturnUrl  = ViewBag.ReturnUrl }, FormMethod.Post, new { @class = "form-horizontal", role = "form" }))

{
    @Html.AntiForgeryToken()
    @Html.DropDownList("dropdownMonths",null, new { style = "width: 200px;" })
    @Html.DropDownList("dropdownYears", null, new { style = "width: 200px;" })

    <input type="submit" value="GO" class="btn btn-default" /> @*Post "GO" button that does not work!!*@


        <div id="detailsDiv">
            @foreach (var AccountGroup in Model )
            {
                <p><h1>@AccountGroup.Key</h1></p>
                foreach (var item in AccountGroup)
                {
                    <p>
                        @*@Html.ActionLink(@item.DocDate.ToShortDateString(), "GetStatement", "Statements", new {id= @ViewBag.UserID, statementDate = @item.DocDate.ToShortDateString(), acctNumber = AccountGroup.Key.ToString() }, new { @class = "form-control, col-sm-6,  medwidth" })
                        @Html.ActionLink("View", "ViewPDF", new { target = @item.strURL })*@
                        <a href="@item.strURL.ToString()" target="_blank">@item.DocDate.ToString("MMM yyyy") Statement</a>
                    </p>
                }
            }       
         </div>

My "Statements/GetStatement" controller (returned from this view) -- This does not get recognized!!

    public ActionResult GetStatement(IOrderedEnumerable<IGrouping<string, AodNetIntegration.Models.DocumentViewModel>> model, string returnUrl)
    {//DO Stuff
    }

My GO button does not call the Controller Method unless I change it to a regular model... is there a way to return > to the controller by posting the page? If not, what is the best way to do this. I would like to do this via AJAX also so I can do a partial post, but it seems I have to figure the posting out first. I've looked at this and this, but cannot quite figure out what I'm missing! Thanks!