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Reinsurance - Narrative (Details) - USD ($) | 3 Months Ended | 9 Months Ended
--- | --- | ---
Mar. 31, 2021 | Sep. 30, 2020 | Sep. 30, 2019 | Sep. 30, 2020 | Sep. 30, 2019
Effects of Reinsurance [Line Items] |  |  |  |  |
Ceded premiums |  | $ 47,173,000 | $ 28,440,000 | $ 144,489,000 | $ 100,260,000
Quota Share Reinsurance Agreement, 2020 |  |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |  |
Contingent termination fee |  |  |  | $ 0 |
Threshold for private mortgage insurer eligibility requirements for termination election (less than) (as a percent) |  |  |  | 90.00% |
Quota share for all policies covered (as a percent) |  |  |  | 30.00% |
Cede rate, option 1 (as a percent) |  |  |  | 25.00% |
Cede rate, option 2 (as a percent) |  |  |  | 20.00% |
Ceding commission, percentage (as a percent) |  |  |  | 20.00% |
Loss ratio threshold for profit commissions (as a percent) |  |  |  | 62.00% |
Credit Union Quota Share Reinsurance Agreement |  |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |  |
Threshold for private mortgage insurer eligibility requirements for termination election (less than) (as a percent) |  |  |  | 80.00% |
Quota share for all policies covered (as a percent) |  |  |  | 65.00% |
Ceding commission, percentage (as a percent) |  |  |  | 20.00% |
Loss ratio threshold for profit commissions (as a percent) |  |  |  | 50.00% |
Quota Share Reinsurance Agreements, Excluding Captive Agreements |  |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |  |
Annual loss ratio cap under quota share reinsurance transactions (as a percent) |  |  |  | 300.00% |
Lifetime loss ratio cap under quota share reinsurance transactions (as a percent) |  |  |  | 200.00% |
Excess of Loss Reinsurance Agreement, Home Re |  |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |  |
Ceded premiums |  | $ 3,700,000 | $ 5,400,000 | $ 12,800,000 | $ 12,400,000
Forecast | Quota Share Reinsurance Agreement, 2021 |  |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |  |
Contingent termination fee | $ 0 |  |  |  |
Threshold for private mortgage insurer eligibility requirements for termination election (less than) (as a percent) | 90.00% |  |  |  |
Quota share for all policies covered (as a percent) | 17.50% |  |  |  |
Cede rate, option 1 (as a percent) | 14.50% |  |  |  |
Cede rate, option 2 (as a percent) | 12.00% |  |  |  |
Loss ratio threshold for profit commissions (as a percent) | 62.00% |  |  |  |
Financial Asset Equal To Or Greater Than 60 Days Past Due | Excess of Loss Reinsurance Agreement, Home Re |  |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |  |
Percent of delinquent reinsured loans to total reinsured loans |  |  |  | 4.00% |

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- Definition The lifetime maximum ratio of non-life losses and loss expenses to non-life net premiums earned under our quota share reinsurance transactions. + References No definition available. + Details
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- Definition The percent of delinquent reinsured principal balance of loans to total reinsured principal balance of loans that causes a trigger event if exceeded. + References No definition available. + Details
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