Note 1 - Condensed Consolidated Financial Statements - Business Overview and Significant Accounting Policies Business Overview and Significant Accounting Policies(Details)		3 Months Ended		6 Months Ended			12 Months Ended
		Jun. 30, 2018 USD ($) $ / shares shares	Jun. 30, 2017 USD ($)	Dec. 31, 2018 USD ($)	Jun. 30, 2018 USD ($) segment $ / shares shares	Jun. 30, 2017 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Aug. 09, 2017 USD ($)
Basis of Presentation and Business Overview [Line Items]
Deposit Assets		$ 88,557,000			$ 88,557,000			$ 88,557,000
Business Overview [Abstract]
Number of Operating Segments | segment					2
Mortgage Insurance [Abstract]
Restructuring and other exit costs		925,000	$ 0		$ 1,476,000	$ 0
Income Tax Expense (Benefit) Recorded as a Result of Finalized IRS Settlement		73,600,000
Qualified Deposit Assets With The U.S. Department Of Treasury Expected to be Submitted		31,000,000			31,000,000
Restructuring and other exit costs - cash payments		1,000,000
Reduction to Available Holding Company Liquidity		$ (31,000,000)			$ (31,000,000)
Mortgage Insurance Segment
Mortgage Insurance [Abstract]
Private Mortgage Insurance Protects Lenders For Loans Made With Less Than This Maximum Down Payment Percentage		20.00%			20.00%
Private Mortgage Insurance Protects Lenders For Refinancings Made to Home Buyers With Less Than This Maximum Equity-Ownership Percentage		20.00%			20.00%
Mortgage and Real Estate Services Segment [Member]
Mortgage Insurance [Abstract]
Restructuring and other exit costs	[1]	$ 1,055,000	0		$ 1,580,000	0
Net Premiums Earned and Net Investment Income		2,400,000			2,402,000
Provision for Doubtful Accounts		0	0		0	0
Total Primary Insurance Mortgage Insurance Products [Member] | Mortgage Insurance Segment
Mortgage Insurance [Abstract]
Risk In Force		$ 53,900,000,000			$ 53,900,000,000
Third Quarter 2017 Repurchase Program [Member]
Mortgage Insurance [Abstract]
Stock Repurchase Program, Authorized Amount									$ 50,000,000
Stock Repurchased During Period, Shares | shares		2,491,843			3,022,856
Accelerated Share Repurchases, Final Price Paid Per Share | $ / shares		$ 16.07			$ 16.56
Stock Repurchase Program, Remaining Authorized Repurchase Amount		$ 0			$ 0
Scenario, Forecast [Member]
Mortgage Insurance [Abstract]
Restructuring and other exit costs				$ 1,400,000			$ 2,900,000
Restructuring and other exit costs - cash payments				$ 1,100,000
Scenario, Forecast [Member] | Asset Impairment Charges [Member]
Mortgage Insurance [Abstract]
Restructuring and other exit costs							200,000
Scenario, Forecast [Member] | Employee Severance and Benefit Costs [Member]
Mortgage Insurance [Abstract]
Restructuring and other exit costs							1,000,000
Scenario, Forecast [Member] | Facility and Lease Termination Costs [Member]
Mortgage Insurance [Abstract]
Restructuring and other exit costs							1,500,000
Scenario, Forecast [Member] | Contract Termination and Other Restructuring Costs [Member]
Mortgage Insurance [Abstract]
Restructuring and other exit costs							$ 200,000
Accounting Standards Update 2016-01 [Member]
Basis of Presentation and Business Overview [Line Items]
Increase in Invested Assets					2,300,000
Accounting Standards Update 2016-01 [Member] | AOCI Attributable to Parent [Member]
Basis of Presentation and Business Overview [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption		224,000	0		224,000	0
Accounting Standards Update 2016-01 [Member] | Retained Earnings [Member]
Basis of Presentation and Business Overview [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption		2,061,000	0		2,061,000	0
Accounting Standards Update 2018-02 [Member] | AOCI Attributable to Parent [Member]
Basis of Presentation and Business Overview [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption		2,724,000	0		2,724,000	0
Accounting Standards Update 2018-02 [Member] | Retained Earnings [Member]
Basis of Presentation and Business Overview [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption		(2,724,000)	$ 0		(2,724,000)	$ 0
Unrealized Loss Related to Equity Securities [Member] | Accounting Standards Update 2016-01 [Member] | Retained Earnings [Member]
Basis of Presentation and Business Overview [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption		(200,000)			(200,000)
Practical Expedient to Measure Certain Other Investments Using the NAV [Member] | Accounting Standards Update 2016-01 [Member] | Retained Earnings [Member]
Basis of Presentation and Business Overview [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption		$ 2,300,000			$ 2,300,000

[1] Does not include impairment of long-lived assets and loss from the sale of a business line, which is not a component of adjusted pretax operating income.