Value Was Either Too Large Or Small For Decimal

When I try and run the program I get an error stating
"Value was either too large or too small for a Decimal."
On the line that says
principal = payment - InterestPaid
I've included the rest of the code as well. Perhaps this is a downside of staring at the screen for so long.

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim payment As Double
Dim result As String
'declarations
[Code] .....