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Statutory Information (Details) | 12 Months Ended
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Dec. 31, 2017 USD ($) jurisdiction | Dec. 31, 2016 USD ($) | Dec. 31, 2015 USD ($)
Statutory Capital [Abstract] |  |  |
Percentage of premiums earned required to be maintained as contingency loss reserves (in hundredths) | 50.00% |  |
Period that contingency loss reserves must be held (in years) | 10 years |  |
Percentage of net premiums earned that incurred losses must exceed to enable early withdrawals from contingency loss reserves (in hundredths) | 35.00% |  |
Related Party Transaction [Line Items] |  |  |
Statutory net income (loss) | $ 310,776,000 | $ 106,326,000 | $ (72,767,000)
Statutory policyholders' surplus | 1,622,115,000 | 1,506,475,000 | 1,608,214,000
Contingency reserve | $ 1,896,701,000 | 1,360,088,000 | 826,706,000
Statutory capital requirements [Abstract] |  |  |
Number of jurisdictions with risk-to-capital requirements | jurisdiction | 16 |  |
Maximum permitted risk-to-capital ratio commonly applied | 25 to 1 |  |
Risk-to-capital ratio on a combined basis at end of period | 10.5 to 1 |  |
Risk-to-capital ratio on combined insurance operations | 10.5 |  |
Percentage of statutory policyholders surplus used to determine maximum allowable dividends | 10.00% |  |
Maximum |  |  |
Statutory capital requirements [Abstract] |  |  |
Risk to capital ratio | 25 |  |
Other Insurance Subsidiaries |  |  |
Related Party Transaction [Line Items] |  |  |
Dividends paid to the parent company |  |  | 6,500,000
Distributions from other insurance subsidiaries to the parent company | $ 0 | 52,001,000 | 38,500,000
Mortgage Guaranty Insurance Corporation |  |  |
Related Party Transaction [Line Items] |  |  |
Loss ratio | 5.00% |  |
Additions to the surplus of MGIC from parent company funds | $ 0 | 36,025,000 | 0
Dividends paid to the parent company | $ 140,000,000 | $ 64,000,000 | $ 0
Statutory capital requirements [Abstract] |  |  |
Risk to capital ratio | 9.5 |  |
Risk to capital ratio at end of period | 9.5 to 1 |  |
Amount of policyholders position above or below required MPP | $ 2,100,000,000 |  |
Amount of required MPP | $ 1,200,000,000 |  |
Adjusted statutory net income measurement period | 3 years |  |
Adjusted statutory net income dividend payment measurement period | 2 years |  |
Adjustment to statutory net income | $ 473,000,000 |  |

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- Definition The amount by which the entity's policyholders position (the insurer's net worth or surplus, contingency reserve and a portion of the reserves for unearned premiums) was above or below the required regulatory minimum of the entity's domiciliary state. + References No definition available. + Details
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- Definition The amount of minimum policyholder position (MPP) required by the entity's domiciliary state. + References No definition available. + Details
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- Definition Cash Distributions Paid To Parent Company + References No definition available. + Details
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- Definition An amount of money established from retained earnings to allow for unforeseen losses in business. Amount of reserves for future policy claims payable and loss expenses to be incurred. + References No definition available. + Details
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- Definition The number of jurisdictions that require a mortgage insurer to maintain a minimum amount of statutory capital relative to the risk in force (or a similar measure) in order for the mortgage insurer to continue to write new business. This is generally referred to as a risk-to-capital requirement. + References No definition available. + Details
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- Definition The percentage of net premiums earned that incurred losses must exceed in a calendar year to allow a mortgage guaranty insurance company to make early withdrawals from the contingency loss reserve with regulatory approval. + References No definition available. + Details
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- Definition The percentage of premiums earned that is required to be maintained as contingency loss reserves by mortgage guaranty insurance companies under statutory accounting practices. + References No definition available. + Details
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- Definition The percentage of statutory policyholders' surplus, as defined, as of the preceding calendar year end which is used in the determination of the maximum allowable dividends that the insurance subsidiaries may pay in any twelve-month period without regulatory approval by the Office of the Commissioner of Insurance of the State of Wisconsin. + References No definition available. + Details
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- Definition The length of time during which contingency loss reserves cannot be withdrawn under statutory accounting practices except as permitted by insurance regulations. + References No definition available. + Details
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- Definition The entity's risk-to-capital ratio as of the end of the reporting period. + References No definition available. + Details
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- Definition The risk-to-capital ratio of the entity's combined insurance operations, including its reinsurance affiliates, as of the end of the reporting period. + References No definition available. + Details
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- Definition Statutory Accounting Practices, Statutory Amount Available For Dividend Payments Without Regulatory Approval, Measurement, Measurement Period + References No definition available. + Details
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- Definition Statutory Accounting Practices, Statutory Amount Available for Dividend Payments without Regulatory Approval, Measurement, Dividend Payment Period + References No definition available. + Details
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- Definition Statutory Accounting Practices, Statutory Net Income, Adjustment + References No definition available. + Details
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- References No definition available. + Details
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- Definition Statutory Capital Requirements, Risk To Capital Ratio + References No definition available. + Details
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- Definition Statutory Capital Requirements, Risk To Capital Ratio For Combined Insurance Operations + References No definition available. + Details
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- Definition Additions to the surplus of a subsidiary from parent company funds. + References No definition available. + Details
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- Definition This element represents disclosure of the total aggregate cash dividends paid to the entity by consolidated subsidiaries, by unconsolidated subsidiaries, and by 50% or less owned persons accounted for using the equity method. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-04(b)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24072-122690 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 235 -Section S99 -Paragraph 2 -Subparagraph (SX 210.9-06) -URI http://asc.fasb.org/extlink&oid=6882215&loc=d3e537971-122884 + Details
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- Definition For insurance companies, a description of the minimum regulatory capital requirements imposed by state insurance regulators, and restrictions on dividend payments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 505 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6486098&loc=d3e24708-158529 + Details
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- Definition Ratio of non-life losses and loss expenses to non-life net premiums earned. + References No definition available. + Details
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- Definition The amount of statutory capital and surplus (stockholders' equity) as of the balance sheet date using prescribed or permitted statutory accounting practices (rather than GAAP, if different) of the state or country. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(23)(c)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6486098&loc=d3e24708-158529 + Details
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- Definition Amount of net income for the period determined using accounting principles prescribed or permitted by insurance regulators. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(23)(c)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 + Details
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