Note 1 - Description of Business and Recent Developments Mortgage Insurance (Details) - Mortgage Insurance Segment $ in Billions	Dec. 31, 2019 USD ($)
Business Overview [Abstract]
Private Mortgage Insurance Protects Lenders For Loans Made With Less Than This Maximum Down Payment Percentage	20.00%
Private Mortgage Insurance Protects Lenders For Refinancings Made to Home Buyers With Less Than This Maximum Equity-Ownership Percentage	20.00%
Insurance in Force	$ 240.6
Risk In Force	$ 60.9