Arithmetic overflow error converting expression to data type int.

string startdate, enddate;
        startdate = StartDate.Text;
        enddate = EndDate.Text;

       
        SqlCommand cmd = new SqlCommand("Usp_QueueMISReport", con);
        cmd.CommandType = CommandType.StoredProcedure;
        DbParameter parm = cmd.CreateParameter();
        parm.ParameterName = "@StartDate";
        parm.Value = StartDate.Text;
        parm.DbType = DbType.String;
        cmd.Parameters.Add(parm);
        parm = cmd.CreateParameter();
        parm.ParameterName = "@EndDate";
        parm.Value = EndDate.Text;
        parm.DbType = DbType.String;
        cmd.Parameters.Add(parm);
        parm = cmd.CreateParameter();
        parm.ParameterName = "@DetailType";
        parm.Value = RADIOBUTTONLIST.SelectedValue;
        parm.DbType = DbType.Int32;
        cmd.Parameters.Add(parm);
        
        try
        {
            con.Open();
            SqlDataAdapter da = new SqlDataAdapter(cmd);
            da.Fill(dt);
            GridView1.DataSource = (dt);
            GridView1.DataBind();
            cmd.ExecuteNonQuery();
        }
        catch (Exception ex)
        {
            throw new Exception("Execption adding account. " + ex.Message);
        }
        finally
        {
            con.Close();

        }
       
    }

}

ALTER PROCEDURE [dbo].[Usp_QueueMISReport]
	-- Add the parameters for the stored procedure here
	@StartDate varchar(20),
	@EndDate   varchar(20),
	@DetailType int =0
AS
BEGIN
-- @detailType Param Explain as follows
-- 1 is For mothly
-- 2 is For Daily
-- 3 is for hourly

Select
     Case when @DetailType = 1 then CONVERT(VARCHAR(20), Min(RectificationTime), 106) + ' To ' + CONVERT(VARCHAR(20), Max(RectificationTime), 106)
             when @DetailType = 0 then CONVERT(VARCHAR(20), Min(RectificationTime), 106) + ' To ' + CONVERT(VARCHAR(20), Max(RectificationTime), 106)
             when @DetailType = 3 then CONVERT(VARCHAR(20), Min(RectificationTime), 106)  
             else ''
             end												      AS [Date]
        ,Case when @DetailType = 3 then CONVERT(VARCHAR(20), Min(RectificationTime), 108) + ' To ' + CONVERT(VARCHAR(20), Max(RectificationTime), 108) 
              else ''
              end												      AS [Interval]
	 ,COUNT(Distinct FetchId)														AS [COMPLAINTS RECEIVED]
	 ,SUM(CLOSED)																	AS [COMPLAINTS CLOSED BY IVR]
	 ,Cast((SUM(ResponseTime)/SUM(isRsponse)) AS decimal(18,2))						AS [AVG RESPONSE TIME]
	 ,dbo.SecToTime(Avg(RectificationDIFF))											AS [AVG TAT]
	 ,Cast (Avg(TotalTries) AS decimal(18,2))										AS [AVG TOTAL NUMBER OF  OF TRIES]
	 ,SUM(SuccessCount)																AS [TOTAL NUMBER OF SUCCESSFUL ATTEMPTS	]
	 ,SUM(unSuccessCount)							                                AS [TOTAL  NUMBER OF UNSUCCESSFUL ATTEMPTS]
	 ,STR(Cast(((SUM(SuccessCount)/Sum(TotalTries))*100) AS decimal(8,2)),8,2)+ '%' AS [AVERAGE # OF SUCCESSFUL ATTEMPTS]
	 ,STR(Cast(((SUM(SuccessCount)/Sum(TotalTries))*100) AS decimal(8,2)),8,2)+ '%' AS [SUCCES RATIO (%)]
	 
	

FROM 

(
					Select TF.FetchId
							,DATEDIFF(SECOND,Tf.DateTimeOfFetch,TF.RectificationTime)				  AS RectificationDIFF
							,TF.RectificationTime													  AS RectificationTime
							,cast(SUM (1) AS decimal(18,2)) TotalTries
							,sum(		CASE  WHEN DA.ResultId IN(5,7,8,9,10,12,13,14)THEN 0
										WHEN DA.ResultId = 4 and TF.DispositionId = 2 THEN 0
										ELSE 1 
										END)                                                          AS SuccessCount
							,sum(		CASE  WHEN DA.ResultId IN(5,7,8,9,10,12,13,14)THEN 1
											 WHEN DA.ResultId = 4 and TF.DispositionId = 2 THEN 1
										ELSE 0 
										END )                                                         AS UnSuccessCount
							,CASE  WHEN TF.DispositionID IN(1,2,3,4,5,8,10) THEN 1 ELSE 0 end		  AS closed
							,sum(CASE  WHEN DA.Resultid =1 and ISNUMERIC(DA.subcode) = 1 THEN DA.subcode ELSE 0 end)				  AS ResponseTime
							,sum(CASE  WHEN DA.Resultid =1 THEN 1 ELSE 0 end)						  AS isRsponse
			from DialAttempts DA
			inner join TicketFetch  TF on DA.FetchId = tf.FetchId
			Inner join Dispositions DP on tf.DispositionId = DP.DispositionId
			inner join DialResult   DR on DA.ResultId = DR.ResultId
			WHERE 
			RectificationTime >= @StartDate
			and
     		RectificationTime <= @EndDate
			and 
			Tf.DispositionId !=  12

			group by TF.FetchId,Tf.DateTimeOfFetch,TF.RectificationTime,TF.DispositionId
)  as FetchDetail

GROUP BY
 CASE  WHEN @DetailType > 0  THEN  Year(RectificationTime)  end , -- For Monthly (1)
 CASE  WHEN @DetailType > 0  THEN  Month(RectificationTime) end , -- For Monthly (1)
 CASE  WHEN @DetailType > 1  THEN  Day(RectificationTime) end ,   -- For Daily   (2)
 CASE  WHEN @DetailType > 2  THEN  DatePart(Hour,RectificationTime)end -- For Hourly(3)
Order by MIN(RectificationTime) ASC
END