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Note 1 - Condensed Consolidated Financial Statements - Business Overview and Significant Accounting Policies Business Overview and Significant Accounting Policies(Details) $ in Thousands, shares in Millions |  | 3 Months Ended | 9 Months Ended | 12 Months Ended | 15 Months Ended |  |
--- | --- | --- | --- | --- | --- | --- | ---
Jan. 27, 2017 USD ($) shares | Sep. 30, 2017 USD ($) | Jun. 30, 2017 USD ($) | Sep. 30, 2016 USD ($) | Sep. 30, 2017 USD ($) segment | Sep. 30, 2016 USD ($) | Sep. 30, 2018 USD ($) | Dec. 31, 2016 USD ($) | Sep. 30, 2018 USD ($) | Aug. 09, 2017 USD ($) | Dec. 31, 2015 USD ($)
Basis of Presentation and Business Overview [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Securities Lending Rate of Collateral Required |  |  |  |  |  | 1.02 |  |  |  |  |  |  |  |
Business Overview [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of Operating Segments | segment |  |  |  |  |  | 2 |  |  |  |  |  |  |  |
Mortgage Insurance [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss on induced conversion and debt extinguishment |  | $ (45,766) |  | $ (17,397) |  | $ (51,469) |  | $ (75,075) |  |  |  |  |  |
Restructuring and other exit costs |  | 12,038 |  | 0 |  | 12,038 |  | 0 |  |  |  |  |  |
Restructuring and other exit costs - cash payments |  | 5,400 |  |  |  |  |  |  |  |  |  |  |  |
Impairment of goodwill (Note 6) |  | 0 |  | 0 |  | 184,374 |  | 0 |  |  |  |  |  |
Finite-Lived Intangible Assets, Net |  | $ 56,045 |  |  |  | $ 56,045 |  |  |  |  |  |  |  |
Repurchase Agreements, Securities Lending Transactions, and Repurchase-to-Maturity Transactions Accounted for as Secured Borrowings, Description of Potential Risks |  |  |  |  |  | Under our securities lending agreements, the Borrower generally may return the loaned securities to us at any time, which would require us to return the collateral within the standard settlement period for the loaned securities on the principal exchange or market in which the securities are traded. We manage this liquidity risk associated with cash collateral by regularly monitoring our available sources of cash and collateral to ensure we can meet short-term liquidity demands in both normal and stressed scenarios. We may use our general liquidity resources to meet any potential cash demands when loaned securities are returned to us. The credit risk under these programs is reduced by the amounts of collateral received. On a daily basis, the value of the underlying securities that we have loaned to the Borrowers is compared to the value of cash and securities collateral we received from the Borrowers, and additional cash or securities are requested or returned, as applicable. In addition, we are indemnified against counterparty credit risk by the intermediary. |  |  |  |  |  |  |  |
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 |  | 0.20 |  |  |  | 0.20 |  |  |  |  |  |  |  |
Risk In Force |  | $ 51,200,000 |  |  |  | $ 51,200,000 |  |  |  |  |  |  |  |
Mortgage and Real Estate Services Segment [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Mortgage Insurance [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Restructuring and other exit costs |  | 5,463 |  | $ 0 | [1] | 5,463 | [1] | $ 0 | [1] |  |  |  |  |
Impairment of goodwill (Note 6) |  |  | $ 184,400 |  |  | 184,374 |  |  |  |  | $ 0 |  |  |
Impairment of Intangible Assets, Finite-lived |  |  | 15,800 |  |  |  |  |  |  |  |  |  |  |
Goodwill |  | 10,922 |  |  |  | 10,922 |  |  |  |  | 195,170 |  |  | $ 195,170
Finite-Lived Intangible Assets, Net |  | 56,045 |  |  |  | 56,045 |  |  |  |  | $ 81,058 |  |  |
Convertible Senior Notes Due 2017 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Mortgage Insurance [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Repayments of Convertible Debt |  |  | 31,600 |  |  |  |  |  |  |  |  |  |  |
Convertible Senior Notes Due 2019 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Mortgage Insurance [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Repurchase Amount | $ 68,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Repayments of Convertible Debt | 110,100 |  |  |  |  |  |  |  |  |  |  |  |  |
Loss on induced conversion and debt extinguishment | $ (4,500) |  |  |  |  |  |  |  |  |  |  |  |  |
Senior Notes [Member] | Senior Notes Due 2024 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Mortgage Insurance [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  | 450,000 |  |  |  | 450,000 |  |  |  |  |  |  |  |
Senior Notes [Member] | Senior Notes Due 2019 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Mortgage Insurance [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  | 300,000 |  |  |  | 300,000 |  |  |  |  |  |  |  |
Debt Instrument, Repurchase Amount |  | 141,400 |  |  |  | 141,400 |  |  |  |  |  |  |  |
Senior Notes [Member] | Senior Notes Due 2021 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Mortgage Insurance [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Repurchase Amount |  | 152,300 |  |  |  | 152,300 |  |  |  |  |  |  |  |
Senior Notes [Member] | Senior Notes due 2019, 2020, and 2021 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Mortgage Insurance [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss on induced conversion and debt extinguishment |  | (45,800) |  |  |  |  |  |  |  |  |  |  |  |
Senior Notes [Member] | Senior Notes Due 2020 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Mortgage Insurance [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Repurchase Amount |  | 115,900 |  |  |  | $ 115,900 |  |  |  |  |  |  |  |
Convertible Debt | Convertible Senior Notes Due 2017 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Mortgage Insurance [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Repurchase Amount |  |  | 21,600 |  |  |  |  |  |  |  |  |  |  |
Loss on induced conversion and debt extinguishment |  |  | $ (1,200) |  |  |  |  |  |  |  |  |  |  |
Convertible Debt | Convertible Senior Notes Due 2019 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Mortgage Insurance [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Reduction in Dilutive Shares Attributable to Redemption of Conversion of Debt Securities | shares | 6.4 |  |  |  |  |  |  |  |  |  |  |  |  |
Total Primary Insurance Mortgage Insurance Products [Member] | Mortgage Insurance Segment |  |  |  |  |  |  |  |  |  |  |  |  |  |
Mortgage Insurance [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Concentration Risk, Percentage |  |  |  |  |  | 98.20% |  |  |  |  |  |  |  |
Pool Insurance Mortgage Insurance Product [Member] | Mortgage Insurance Segment |  |  |  |  |  |  |  |  |  |  |  |  |  |
Mortgage Insurance [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Concentration Risk, Percentage |  |  |  |  |  | 1.60% |  |  |  |  |  |  |  |
Third Quarter 2017 Repurchase Program [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Mortgage Insurance [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stock Repurchase Program, Authorized Amount |  |  |  |  |  |  |  |  |  |  |  |  | $ 50,000 |
Hurricanes Harvey and Irma [Member] | Mortgage Insurance Segment |  |  |  |  |  |  |  |  |  |  |  |  |  |
Mortgage Insurance [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Concentration Risk, Percentage |  |  |  |  |  | 8.80% |  |  |  |  |  |  |  |
Risk In Force |  | $ 4,400,000 |  |  |  | $ 4,400,000 |  |  |  |  |  |  |  |
Securities Financing Transaction, Fair Value [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Basis of Presentation and Business Overview [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Securities Lending Rate of Collateral Required |  |  |  |  |  | 1.00 |  |  |  |  |  |  |  |
Scenario, Forecast [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Mortgage Insurance [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Restructuring and other exit costs |  |  |  |  |  |  |  |  |  | $ 7,500 |  | $ 19,500 |  |
Restructuring and other exit costs - cash payments |  |  |  |  |  |  |  |  |  | $ 6,000 |  |  |  |
Scenario, Forecast [Member] | Asset Impairment Charges [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Mortgage Insurance [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Restructuring and other exit costs |  |  |  |  |  |  |  |  |  |  |  | 8,100 |  |
Scenario, Forecast [Member] | Employee Severance and Benefit Costs [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Mortgage Insurance [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Restructuring and other exit costs |  |  |  |  |  |  |  |  |  |  |  | 6,900 |  |
Scenario, Forecast [Member] | Facility and Lease Termination Costs [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Mortgage Insurance [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Restructuring and other exit costs |  |  |  |  |  |  |  |  |  |  |  | 2,700 |  |
Scenario, Forecast [Member] | Contract Termination and Other Restructuring Costs [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Mortgage Insurance [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Restructuring and other exit costs |  |  |  |  |  |  |  |  |  |  |  | $ 1,800 |  |
[1] | Primarily includes employee severance and related benefit costs. Does not include impairment of long-lived assets, which is not considered a component of adjusted pretax operating income.

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- Definition This element represents the maximum down payment percentage on a home's purchase price that is used to measure the need for private mortgage insurance. + References No definition available. + Details
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