WPF Datagrid Binding Doesn't Update Until Clicking Row Header

I have a datagrid that is bound to a List in the view model. The grid's contents don't update until I click on the row header. Clicking in various cells doesn't affect it. I have to click on the header.

This is the datagrid in the XAML:

<DataGrid x:Name="TransactionDetailsGrid" Grid.Row="1" AutoGenerateColumns="False" SelectionMode="Extended" IsReadOnly="True" HeadersVisibility="Column"
                  ItemsSource="{Binding TransactionDetailList}" SelectedItem="{Binding SelectedTransactionDetail}" GridLinesVisibility="None">
    <DataGrid.Columns>
        <DataGridTextColumn Binding="{Binding Path=Account.AccountNumber}" Header="Account No." HeaderStyle="{StaticResource DataGridHeaderStyleCenter}" Width="120" />
        <DataGridTextColumn Binding="{Binding Path=Account.AccountName}" Header="Account Name" HeaderStyle="{StaticResource DataGridHeaderStyleCenter}" Width="*" />
        <DataGridTextColumn Binding="{Binding Path=Amount}"  Header="Amount" HeaderStyle="{StaticResource DataGridHeaderStyleCenter}" Width="120" />
    </DataGrid.Columns>
</DataGrid>

And this is from the view model:

public List<TransactionDetail> TransactionDetailList
{
    get { return this._transactionDetailList; }

    set
    {
        this._transactionDetailList = value;
        RaisePropertyChanged("TransactionDetailList");                
    }
}

This is the edit of one of the items, in the view model:

private void AddTransactionDetail()
{
    TransactionDetailViewModel viewModel = new TransactionDetailViewModel();

    MainWindowViewModel.ViewLoader.ShowDialog(viewModel);

    if (viewModel.TransactionDetail != null)
    {
        this.TransactionDetailList.Add(viewModel.TransactionDetail);
        RaisePropertyChanged("TransactionDetailList");
    }
}

After this runs, I can put a breakpoint on the getter of TransactionDetailL