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 TransactionDetailList, and the collection has the item in it. However, the datagrid is empty. If I click on the header row, the item shows up in the grid.

I have the same issue when doing an edit.

I've done this successfully before, so I'm not sure what's different here. Am I missing something obvious? Why won't the grid show its contents until I click on the header row?

I just noticed something interesting. When I click on the grid header, the breakpoint in the TransactionDetailList getter doesn't get hit, but the data still shows up. So, it's like the grid has the info, it's just not showing it until the header is clicked.

After changing to use ObservableCollection, it worked. But now I'm having the same problem with the edit (grid doesn't update until clicking the header):

private void EditTransactionDetail()
{
    TransactionDetailViewModel viewModel = new TransactionDetailViewModel(this.SelectedTransactionDetail);

    MainWindowViewModel.ViewLoader.ShowDialog(new TransactionDetailViewModel(this.SelectedTransactionDetail));

    RaisePropertyChanged("TransactionDetailList");
}

Does my entity need to implement INotifyPropertyChanged? If I change the collection, and call RaisePropertyChanged, shouldn't that cause an update to the grid?